HANDBOOK 


OF 


PLANT    MORPHOLOGY 

BEING  THE 

HANDBOOK   OF    PLANT    DISSECTION 


BY 

J.  C.  ARTHUR,  CHARLES  R.  BARNES 
AND  JOHN  M.  COULTER 


REVISED     AND     REWRITTEN 

BY 

OTIS  W.  CALDWELL,  PH.D. 

Professor  »f  Botany  in  the  Eastern  Illinois  State  Normal  School 


NEW  YORK 

HENRY   HOLT    AND    COMPANY 
1904 


Copyright,  1886, 1904, 

BY 

HENRY  HOLT  AND  COMPANY 


ROBERT  DRUMMOND,    PRINTER,   NSW   YORK. 


SRLF 
YKL 


ANNOUNCEMENT. 

SINCE  1886,  when  the  Handbook  of  Plant  Dissection 
was  published,  both  the  methods  of  laboratory  work  and 
knowledge  of  the  plant  kingdom  have  very  materially 
changed.  The  authors  thought  that  any  demand  for 
the  book  would  have  disappeared  long  since,  but  con- 
tinued sales  have  forced  them  to  the  conclusion  that  in 
justice  to  the  subject  and  also  to  themselves  a  revision  is 
necessary.  In  morphological  instruction  the  very  detailed 
study  of  a  few  types  has  given  place  to  a  study  of  the 
most  significant  features  of  a  considerable  number  of 
types;  and  the  accumulation  of  somewhat  unrelated 
facts  has  been  succeeded  by  the  attempt  to  organize  the 
facts  into  a  connected  account  of  the  evolution  of  the 
plant  kingdom. 

An  adequate  revision,  therefore,  meant  a  complete 
rewriting,  and  this  the  original  authors  were  unable  to 
undertake.  Accordingly  they  have  delegated  it  to  one 
whose  contact  with  laboratory  work  in  elementary  mor- 
phology is  fresher  and  has  proved  to  be  in  every  way 
successful. 

The  book  is  a  new  one,  although  developed  in  accord- 
ance with  the  old  plans,  and  it  will  far  more  worthily 


iv  ANNOUNCEMENT. 

supply  the  demand  that  seems  to  exist  than  could  an 

edition  long  since  out  of  date. 

J.  C.  ARTHUR. 
C.  R.  BARNES. 
J.  M.  COULTER. 

March  10,  1904. 


AUTHOR'S   PREFACE. 

IN  the  preparation  of  these  outlines  it  is  recognized 
that  a  given  set  of  directions  is  not  completely  adequate 
for  the  work  of  any  two  teachers,  nor  even  for  one 
teacher's  use  during  two  consecutive  years.  A  good 
instructor  is  the  chief  determinant  in  a  course  of  study. 
In  his  hands  the  materials,  the  laboratory,  and  the  book 
become  efficient  in  the  presentation  of  the  subject.  To 
his  students  the  laboratory  guide  serves  as  an  outline  to 
which  he  makes  additions  as  determined  by  the  immedi- 
ate needs  of  his  own  class.  It  is  rather  generally  recog- 
nized that  a  course  of  study  in  botany  may  be  made  much 
stronger  if  a  well-organized  plan  is  placed  before  the 
students,  since  a  good  instructor  can  make  requisite 
eliminations  and  additions  to  fit  his  peculiar  needs,  and 
all  by  means  of  the  laboratory  guide  may  have  the  advan- 
tage of  the  accumulated  experience  of  others.  The 
wide  field  of  usefulness  that  was  filled  by  Plant  Dis- 
section furnishes  abundant  evidence  as  to  the  value  of 
a  good  laboratory  guide.  It  was  in  response  to  a  belief 
that  a  new  book  which  embodies  the  general  arrange- 
ment and  some  of  the  important  principles  of  the  old  one 
will  be  correspondingly  useful,  that  the  authors  of  Plant 
Dissection  suggested  the  preparation  of  this  work. 


vi  AUTHOR'S  PREFACE. 

The  outlines  here  included,  subject  to  variations  neces- 
sitated by  peculiarities  of  local  environment,  have  been 
used  by  the  writer  in  courses  given  in  the  University  of 
Chicago,  the  Biological  Station  of  the  University  of 
Indiana,  and  the  Eastern  Illinois  State  Normal  School. 
In  addition  to  this  test  of  use  the  manuscript  has  been 
read  and  improved  in  very  important  ways  by  the  authors 
of  Plant  Dissection,  and  by  Professor  F.  E.  Lloyd  of 
Teachers  College,  New  York,  and  Professor  F.  L. 
Stevens  of  the  State  Agricultural  College,  Raleigh,  N.  C., 
to  all  of  whom  grateful  acknowledgments  are  made. 

OTIS  W.  CALDWELL. 

THE  EASTERN  ILLINOIS  STATE  NORMAL  SCHOOL, 
October  5,  1904. 


CONTENTS. 

PJUM 

I.  Preliminary  Chapter i 

Point  of  View,  i;  Equipment,  2;  Use  of  the 
Laboratory  (Hand  Lenses  and  Compound 
Microscope,  4;  Illustrative  Material,  5 ;  Draw- 
ings, Notes,  etc.,  8;  Reference  Reading,  10; 
Collection  and  Preservation  of  Material,  13; 
Independent  Work,  14). 

II.  Green  Slime  (Pleurococcus  viridis) 16 

III.  Nostoc 21 

IV.  Oscillaria 24 

V.  Ulothrix 29 

VI.  Cladophora 34 

VII.  Spirogyra 38 

VIII.  Vaucheria  sessilis 46 

IX.  Coleochaete 51 

X.  Common  Black  Mold  (Mucor  stolonifer) 55 

XL  Toadstool  (Coprinus  sp.  or  Agaricus  sp.) 59 

XII.  White  Rust  (Albugo  Candida  or  A.  Portulacae).  .  .  62 

XIII.  Mildew  (Microsphcera  Friesii,  or  M.  Quercf) 69 

XIV.  A  Lichen 75 

XV.  Liverwort  (Riccia) 80 

XVI.  Marchantia  polymorpha 85 

XVII.  A  Leafy  Liverwort  (Porella) 92 

XVIII.  Anthoceros 95 

XIX.  A  Moss-plant  (Atrichum  undulatum  or  Funaria 

hygrometrica) 99 

XX.  The  Bracken  Fern  (Pteris  aquilina) 107 

XXI.  Scouring-rush,  or  Horsetail  (Equisetum  arvense)..  117 

XXII.  Club-moss  (Selaginella  sp.) 122 

XXIII.  Pine  (Pinus  Austriaca  or  P.  Laricio) 129 

vii 


viii  CONTENTS. 

XXIV.  Wake-robin  (Trillium  sp.) 145 

XXV.  Buttercup  (Ranunculus  sp.) 158 

XXVI.  Shepherd's-purse  (Capsella  Bursa-pastoris) 163 

XXVII.  Sunflower  (Helianthus  annuus) 167 

XXVIII.  Glossary  of  Terms 173 

XXIX.  Index 187 


INTRODUCTION. 

I.  POINT  OF  VIEW. 

In  preceding  school  work  the  student  is  expected  to 
have  obtained  some  general  notions  as  to  what  plants  are, 
and  as  to  the  way  in  which  they  are  adjusted  to  environ- 
ment in  structure  and  habit.  In  the  organization  of  a 
more  formal  course  in  botany,  it  is  believed  that  two  pro- 
minent facts  should  be  kept  in  mind.  First,  structures 
of  plants  are  related  and  more  or  less  perfectly  adapted 
to  the  two  primary  functions  of  nutrition  and  reproduction. 
Second,  there  has  been  throughout  the  history  of  the 
plant  kingdom  a  gradual  evolution  of  plants  as  their 
structures  have  become  progressively  better  adapted  to  the 
two  phases  of  plant  work.  In  the  general  course  in 
botany  plant  structures  are  considered  from  the  point  of 
view  of  what  they  have  to  do  in  nutrition  and  reproduc- 
tion, and  with  reference  to  the  general  problem  of  evolu- 
tion of  the  plant  kingdom.  In  tracing  out  these  two 
lines  of  plant  activity  a  considerable  knowledge  of  in- 
dividual plants  and  of  the  various  groups  of  plants  will 
be  obtained. 

The  general  course  in  botany  should  not  be  planned 
primarily  with  the  idea  of  training  specialists  in  the  sub- 
ject, but  should  present  those  essential  principles  of  plant 
life  that  are  adapted  to  the  needs  of  the  general  student 


2  INTRODUCTION. 

who  may  eventually  give  the  major  part  of  his  time  to 
botany  or  to  any  other  subject. 

II.  EQUIPMENT. 

The  laboratory  should  be  provided  with  well  made 
unvarnished  tables,  so  placed  as  to  leave  ample  space  for 
students  to  move  about  the  room.  If  good  light  comes 
from  one  or  two  sides  of  the  room,  the  best  results  may  be 
obtained  by  placing  the  tables  with  their  ends  to  the 
windows.  There  should  be  for  general  use: 

1.  A  supply  of  good  water,  distilled  water  being  prefer- 
able in  many  cases. 

2.  Commercial  alcohol  or  synthol. 

3.  Formalin. 

4.  Glycerin. 

5.  A  five  per  cent  solution  of  potassium  hydroxid  or 
sodium  hydroxid. 

6.  lodin. 

7.  A  cement  for  ringing  mounts.    King's,  or  "gold  size" 
will  be  satisfactory. 

8.  Camel's-hair  brushes. 

9.  A  turntable. 

10.  A  razor-strop. 

11.  A  hone  for  sharpening  razors,  and  another  for  scal- 
pels. 

12.  Two  or  three  vascula. 

13.  Glass  bottles  and  jars  of  various  sizes  for  collecting 
and  preserving  specimens. 

14.  Some  large  glass  jars  for  growing  water-plants  in  the 
laboratory. 

15.  Driers,  plant-press,  and  mounting-paper. 


INTRODUCTION.  3 

In  addition  to  these  things  in  many  laboratories  it  is 
quite  desirable  to  add  materials  with  which  specially  pre- 
pared permanent  mounts  are  made.  Such  a  list  should 
include : 1 

1 6.  A  microtome. 

17.  An  imbedding-oven. 

1 8.  Paraffin. 

19.  Various  reagents,  as    xylol,  clove-oil,   bergamot-oil, 
cedar-oil,  absolute  alcohol,  and  Canada  balsam. 

20.  Stains,  as  Delafield's  haematoxylin,  cyanin,  erythro- 
sin,  iron  alum,  bismarck  brown,  etc. 

21.  Glassware  designed  especially  for  work  in  staining 
and  mounting  microtome  sections. 

Each  student  will  need : 

22.  Hand-lens,  or  dissecting-microscope. 

23.  Compound  microscope. 

24.  Razor. 

25.  Small  pair  of  forceps. 

26.  Dissecting-needles. 

27.  Medicine- dropper,  or  pipette. 

28.  Syracuse  watch-glass,  or  other  small  glass  dish. 

29.  Glass  slides  and  cover-slips. 

30.  Blotting  or  filter  paper. 

31.  A  clean  soft  cloth  for  cleaning  the  microscope  and 
drying    slides  and  cover- slips;    also  lens-paper    for 
cleaning  the  lenses. 

32.  Drawing  materials,  consisting  of  good  paper  and  a 
medium  hard  pencil.    A  fine  pen  such  as  a  litho- 
graphic pen  and  India  ink  may  be  added  with  profit. 

1  For  complete  list  of  things  needed  see  Chamberlain's  "  Methods  in 
Plant  Histology." 


4  INTRODUCTION. 

III.  HOW  TO  USE  THE  LABORATORY. 

i.  Hand-lenses  and  compound  microscope. — All  that 
can  be  determined  concerning  the  specimen  in  hand 
without  magnification  should  be  done  before  use  is  made 
of  magnifying-glasses.  The  use  of  hand  or  dissect- 
ing lenses  and  the  compound  microscope  should  never 
be  considered  an  end  in  itself,  but  merely  a  means  of 
obtaining  a  better  idea  of  plants  than  is  possible  without 
these  things. 

A  prime  requisite  in  the  use  of  any  optical  instrument 
is  cleanliness;  dirty  lenses  frequently  defeat  the  very 
object  of  their  use,  namely,  clearer  vision.  Before  begin- 
ning to  work  with  any  lens,  see  that  it  is  perfectly  clean. 
When  a  lens  needs  cleaning  a  camel's-hair  brush  may 
first  be  used  to  brush  away  any  particles  of  dust.  Then 
wipe  gently  with  a  piece  of  lens-paper  or  unstarched 
linen  or  cotton,  breathing  first  upon  the  lens  to  moisten 
the  dirt.  Too  great  care  cannot  be  taken  to  avoid 
scratching  the  polished  surface  of  the  lens;  hence  in 
wiping  it  the  least  possible  effective  pressure  should  be 
used.  If  properly  handled  after  once  thoroughly  cleaned, 
lenses  will  seldom  need  any  cleaning  except  brushing. 
One  should  avoid  touching  the  lens  with  the  fingers, 
since  the  oil  from  the  skin  adheres  to  the  glass  and 
temporarily  impairs  its  usefulness.  Such  spots  may  be  re- 
moved by  wiping  with  linen  slightly  moistened  with  alco- 
hol. In  using  the  compound  microscope  the  front  only 
of  the  objectives  and  both  surfaces  of  both  lenses  of  the 
eyepieces  need  cleaning.  If  the  eyepiece  be  dirty,  there 
will  be  specks  in  the  field  of  view  when  there  is  no  object 
upon  the  stage.  These  can  be  made  more  apparent  by 


INTRODUCTION.  5 

turning  the  eyepiece  in  the  tube  while  looking  through 
it.  In  like  manner  by  partly  unscrewing  the  eye-lens  and 
turning  it,  one  may  discover  whether  the  eye-lens  or 
field-lens  is  dirty.  If  the  front  lens  be  dirty,  it  will  be 
shown  by  a  dimness  and  want  of  definition  of  the  out- 
lines of  objects,  thus  affecting  the  whole  field  of  view. 

In  focusing,  use  first  the  low- power  objective.  By  using 
the  rack  and  pinion  adjustment  lower  the  objective  well 
down  toward  the  cover-slip.  Then  while  looking  into 
the  eyepiece,  after  having  made  sure  that  the  best  light 
is  reflected  by  the  mirror  up  through  the  diaphragm  in 
the  stage,  slowly  raise  the  objective  until  the  object  comes 
into  view.  When  it  is  desired  to  use  the  high- power 
objective,  carefully  lower  it  until  it  is  almost  in  contact 
with  the  cover-slip.  Then  while  looking  into  the  eyepiece 
focus  upward  until  the  object  is  seen  clearly. 

Some  nosepieces  are  so  constructed  that  when  the 
low  power  is  in  focus  the  high  power  may  be  turned 
directly  into  focus  without  changing  the  elevation  of  the 
objectives.  In  no  case  should  one  focus  downward 
while  looking  into  the  eyepiece  unless  the  object  is  al- 
ready in  view.  Failure  to  observe  this  caution  may 
result  in  forcing  an  objective  down  upon  the  slide.  Also, 
before  placing  or  removing  a  slide  the  low- power  objec- 
tive should  be  turned  into  position  for  use. 

Before  leaving  the  laboratory  at  the  close  of  a  labora- 
tory period,  make  sure  that  all  the  instruments  are  thor- 
oughly clean  and  dry  and  in  their  proper  places. 

2.  Illustrative  material.  —  In  studying  plants  in  the 
laboratory  it  must  always  be  kept  in  mind  that  one  should 
find  out  as  much  as  he  can  about  the  structures  and  their 


6  INTRODUCTION. 

relation  to  life  habits,  without  the  use  of  special  instru- 
ments and  reagents.  The  latter  things  are  to  be  called 
into  use  to  extend  the  vision  beyond  its  ordinary  limits- 
If  this  fact  is  not  kept  constantly  in  mind,  the  study  may 
easily  resolve  itself  into  the  mere  manipulation  of  labora- 
tory tools,  or  a  study  of  the  technique  of  instruments 
and  reagents.  A  knowledge  of  these  things  is  helpful  to 
a  high  degree  when  their  proper  use  is  clearly  defined. 

Do  not  dissect  specimens  or  make  sections  until  it  is 
decided  in  a  general  way  what  to  look  for  and  where  to 
look  for  it.  Such  a  general  notion  is  essential  to  proper 
orientation  of  structures. 

When  specimens  are  to  be  mounted  one  must  be  care- 
ful lest  they  become  dry  by  evaporation.  Water  may 
easily  be  placed  upon  a  drying  specimen  that  has  been 
mounted,  by  touching  a  wet  brush  or  a  drop  of  water 
from  a  pipette  at  the  edge  of  the  cover-slip. 

Many  of  the  materials  for  study  may  be  mounted 
entire.  Others  will  need  careful  dissection  by  use  of  the 
needles.  This  dissection  will  often  be  made  much  more 
easy  and  far  more  successful  by  first  boiling  the  material 
for  one  or  two  minutes  in  a  five  per  cent  solution  of  potas- 
sium hydroxid,  then  pouring  off  the  liquid  and  rinsing  in 
water.  Still  others  can  be  studied  only  by  means  of  care- 
fully made  sections.  Some  of  these  sections  should  be 
made  by  use  of  the  microtome,  but  most  of  them  the 
student  can  make  by  free-hand  cutting  with  a  good  razor. 
Very  delicate  materials  may  be  sectioned  by  being  placed 
between  pieces  of  pith.  More  rigid  ones  may  be  held  free 
in  the  hand,  or  in  the  hand-microtome.1 

1  For  methods  of  killing,  imbedding,  sectioning,  staining,  and  mounting 


INTRODUCTION.  ^ 

In  case  good  mounts  are  obtained  and  there  is  not 
time  sufficient  to  complete  the  study  before  the  close  of  the 
laboratory  period,  they  may  be  preserved  by  replacing  the 
water  of  the  mount  by  use  of  a  ten  per  cent  solution  of 
glycerin  in  water.  A  liberal  supply  of  the  solution  should 
be  used,  since  the  water  evaporates,  thus  causing  a  thick- 
ening of  the  glycerin.  Mounts  so  made  may  be  preserved 
for  weeks.  When  the  glycerin  has  become  quite  thick 
these  mounts  may  be  made  permanent  by  "  ringing" 
them  with  cement.  To  do  this  first  remove  the  glycerin 
from  about  the  edge  of  the  cover-slip  by  use  of  a  cloth 
dampened  in  alcohol;  then  place  the  slide  on  the  turn- 
table, and  after  having  put  it  in  motion,  apply  tangentially 
to  the  margin  of  the  cover-slip,  by  means  of  a  camel's- 

the  student  who  expects  to  do  such  work  should  consult  Chamberlain's 
"Methods  in  Plant  Histology"  and  numerous  articles  in  the  "Journal 
of  Applied  Microscopy."  Specific  references  will  be  made  later. 

Unless  the  class  is  to  do  considerable  work  in  histological  technique 
the  laboratory  should  have  ready  for  use  a  set  of  good  slides  of  the 
more  difficult  sections  called  for  in  the  outline.  Sections  of  the  follow- 
ing things  should  be  included,  and  many  others  may  be  added  with  profit : 

1.  The  host  plant  of  the  parasite  Albugo,  illustrating  the  structure  and 
reproduction  of  the  latter. 

2.  The  gametophyte  of  Riccia,  showing  vegetative  structure,  sex-organs, 
and  young  sporophyte. 

3.  Marchantia,   showing  vegetative  structure  of  thallus,  archegonial 
and  antheridial  heads,  and  stages  in  development  of  sporophyte. 

4.  Anthoceros  gametophyte  and  sporophyte. 

5.  Porella  branches  bearing  sex-organs  and  sporophytes. 

6.  Moss,  showing  sex-organs  and  capsule. 

7.  Pteris  or  a  similar  fern,  showing  leaf,  rhizome,  sporangia,  gameto- 
phytes  with  sex-organs,  and  young  sporophytes. 

8.  Marsilia  or  Selaginella,  showing  structures  of  male  and   female 
gametophytes. 

9.  Pine,  showing  wood,   needle-leaf,   microsporangia,  megasporangia, 
with  gametophytes,  and  young  sporophytes. 

10.  Trillium  leaf,   root   (or   onion    root),   stem,  microsporangia,  and 
megasporangia. 

11.  Ranunculus,   microsporangia    megasporangia,  and   stem.     Rumex 
will  serve  as  well. 


8  INTRODUCTION. 

hair  brush,  a  ring  of  the  cement.  Place  the  slide  in  a 
horizontal  position  until  the  cement  is  dry.  A  second 
and  third  application  of  the  cement  helps  to  insure 
perfect  firmness. 

This  method  of  making  permanent  mounts  will  be 
found  useful  with  many  of  the  lower  forms  of  plants  when 
mounted  entire,  and  with  dissections  and  free-hand  sec- 
tions of  the  tissues  of  more  complex  plants.  These 
specimens  may  be  mounted  also  in  Canada  balsam,  a 
method  that  gives  greater  permanency,  but  in  some  cases 
the  manipulation  is  more  difficult.  With  microtome  sec- 
tions balsam  will  be  found  highly  desirable  as  a  mount- 
ing substance. 

In  studying  the  higher  plants  there  will  be  found  from 
time  to  time  specimens  that  illustrate  especially  well  cer- 
tain structures  and  adaptations  to  peculiarities  of  environ- 
ment. It  will  be  of  advantage  to  preserve  some  of  these 
in  the  form  of  herbarium  specimens.  This  may  be  done 
by  drying  the  plants  between  heavy  blotters  especially 
prepared  for  the  purpose,  and  afterwards  mounting  them 
on  heavy  paper. 

By  preserving  entire  plants  and  the  best  prepared 
slides  an  individual  or  a  laboratory  will  soon  accumulate 
a  good  supply  of  illustrative  material.  Both  individuals 
and  laboratories,  however,  must  guard  against  the  danger 
of  collecting  material  that  illustrates  nothing. 

3.  Drawings,  notes ,  etc.  —  In  the  systematic  examina- 
tion of  an  object  two  kinds  of  memoranda,  descriptions 
and  drawings,  should  be  made.  The  value  of  the  for- 
mer is  usually  conceded,  but  that  of  the  latter  is  often 
deemed  too  slight  to  repay  the  trouble.  The  importance 


INTRODUCTION.  9 

of  laboratory  drawing  is  not  likely  to  be  too  strenuously 
urged,  and  the  difficulty  and  tediousness  of  execution, 
which  will  largely  disappear  with  practice,  should  never 
be  offered  as  an  excuse  for  its  neglect. 

Drawings  may  represent  the  object  with  various  degrees 
of  completeness.  At  one  extreme  is  the  diagram,  which 
aims  only  to  give  relative  positions,  sizes,  and  relations 
of  parts.  A  diagram  is  often  very  helpful  at  the  begin- 
ning of  the  study  of  a  specimen.  At  the  other  extreme 
is  the  drawing  that  is  as  close  a  counterpart  of  the  object 
seen  as  the  person  who  draws  it  is  capable  of  producing. 

Drawings  may  usually  be  made  satisfactorily  in  out- 
line with  but  little  shading.  The  best  results  may  be 
obtained  by  making  definite  outlines  first  by  use  of  a 
sharp,  hard  pencil,  then  tracing  the  outlines  and  shading 
with  a  fine  pen  and  good  ink.  The  paper  used  for  draw- 
ing should  be  the  heaviest  linen  ledger-paper  or  (more  ex- 
pensive) bristol-board.  A  convenient  form  is  had  by 
cutting  the  paper  into  pieces  four  by  six  inches.  Note- 
paper  may  be  cut  of  the  same  size,  and  the  two  may  be 
bound  temporarily,  thus  constituting  a  book  to  which 
the  student  adds  at  each  laboratory  period.  Such  blank 
laboratory  books  are  sold  by  reliable  dealers. 

The  approximate  amount  of  magnification,  if  any,  under 
which  the  specimen  was  observed  at  the  time  the  drawing 
was  made  should  always  be  noted  in  connection  with  the 
figure. 

Photographs  may  be  useful  in  illustrating  habitats  and 
individual  characteristics  of  plants  not  readily  observed  by 
the  class.  Both  geographical  and  seasonal  distribution 
of  plant  life  is  such  that  often  it  is  impossible  for  students 


10  INTRODUCTION. 

to  obtain  an  adequate  idea  of  the  normal  environment  of 
the  plants  under  consideration.  If  in  connection  with  the 
work,  instructor  and  students  who  can  do  so,  will  make 
and  preserve  photographs  of  different  phases  of  plant  life, 
each  laboratory  will  soon  possess  a  collection  that  will  add 
much  to  the  general  knowledge  of  the  forms  studied.1 

Laboratory  notes  need  not  be  extensive,  but  should  be 
clear  and  definite,  and  by  means  of  the  descriptions  con- 
tained in  them  and  by  their  constant  reference  to  draw- 
ings, should  constitute  a  brief  presentation  of  the  impor- 
tant features  of  the  particular  plant  in  question.  The 
laboratory  notes  should  be  made  up  in  the  main  of  things 
the  student  has  learned  during  his  study  of  the  plants  them- 
selves. Field  notes  may  well  be  included  with  laboratory 
notes,  but  both  of  these  should  be  kept  separate  from 
those  made  in  connection  with  lectures,  recitations,  and 
readings. 

4.  Reference  reading. — Throughout  the  outlines  occa- 
sional references  are  made  to  sources  of  information  upon 
topics  in  hand.  It  will  not  always  be  possible  for  the 
students  to  look  up  these  references,  and  they  by  no  means 
include  all  that  should  be  read.  Access  should  be  had  to 
some  good  magazines,  such  as  the  Botanical  Gazette, 
Bryolo gist,  Journal  of  Applied  Microscopy,2  Plant  World, 
Rhodora,  Torreya,  Bulletin  of  the  Torrey  Botanical  Club, 
and  the  Journals  of  the  New  York  Botanical  Gardens. 

If  the  following  books  are  available  in  the  library,  the 

1  These  photographs  may  be  made  into  lantern-slides,  or  slides  may 
be  purchased  that  will  illustrate  details  of  plant  structures  and  eco- 
logical relations  of  plants. 

2  The  publication  of  this  journal  has  been  discontinued,  but  the  back 
numbers  may  be  obtained,  and  are  especially  helpful. 


INTRODUCTION.  II 

student  will  be  greatly  helped.     Some  of  them  for  text 
use  are  essential  to  success  in  the  work. 

Atkinson,  G.  F.     Elementary  Botany.     Henry  Holt    &  Co., 

New  York,  1898. 
Bailey,  L.  H.     An  Elementary  Text-book  of  Botany.    The 

Macmillan  Company,  New  York,  1901. 
Barnes,  C.  R.     Plant  Life.     Henry  Holt   &  Co.,  New  York, 

1898. 
Barnes,  C.  R.,  and  Heald,  F.  G.     Analytic  Key  to  the  Genera 

and  Species  of  North  American  Mosses.     The  University 

of  Wisconsin,  Madison,  1896. 
Bergen,  J.  Y.     The  Foundations  of  Botany.     Ginn    &  Co., 

Boston,  1901. 
Britton  and  Brown.     Flora  of  the  Northeastern  United  States 

and  Canada.     Charles  Scribner's  Sons,  New  York,  1898. 
Campbell,  D.  H.     The  Evolution  of  Plants.     The  Macmillan 

Company,  New  York,  1899. 

A  Universal  Text-book   of  Botany.      The  Macmillan 

Company,  New  York,  1902. 

Structure   and   Development   of    Mosses   and   Ferns. 

The  Macmillan  Company,  New  York,  1895. 

Chamberlain,  C.  J.  Methods  in  Plant  Histology.  The  Uni- 
versity of  Chicago  Press,  Chicago,  1901. 

Chapman,  A.  W.  Flora  of  the  Southern  States.  Cambridge 
Botanical  Supply  Co.,  Cambridge,  Mass. 

Coulter  and  Chamberlain.  Seed  Plants,  Part  I.  Gymno- 
sperms.  D.  Appleton  &  Co.,  New  York,  1899. 

Morphology  of  Angiosperms.      D.  Appleton    &  Co., 

New  York,  1903. 

Coulter,  J.  M.  Plant  Structures.  Revised  edition.  D.Apple- 
ton  &  Co.,  New  York,  1904. 

Manual  of  Rocky  Mountain  Botany.     American  Book 

Co.,  New  York. 


12  INTRODUCTION. 

DeBary,  A.  Comparative  Morphology,  and  Biology  of  the 
Fungi,  Mycetozoa,  and  Bacteria.  The  Clarendon  Press, 
Oxford,  1880. 

Goebel,  K.     Organography,  Vols.  I  and  II.     Oxford,  1900. 

Outlines  of    Classification   and   Special   Morphology. 

Oxford,  1887. 

Gray,   Asa.      Manual   of  Botany,    6th    edition.      American 

Book  Co.,  New  York. 
Grout,  A.  J.    Mosses  with  the  Hand-lens.     Published  by  the 

author,  New  York,  360  Lenox  Road,  Flatbush,  1900. 
Pfeffer,  W.     The  Physiology  of  Plants,  translated  by  A.  J. 

Ewart.     2  vols.     Clarendon  Press,  Oxford,  1900. 
Small,  J.  K.     Flora  of  the  Southeastern  States.     Published  by 

the  author,  New  York,  1903. 
Strasburger,  Noll,  Schenck,  and  Schimper.     A  Text-book  of 

Botany,  2d  edition,  translated  by  Long.     The  Macmillan 

Company,  New  York,  1903. 
Underwood,  L.  M.     Our  Native  Ferns  and  their  Allies.  Henry 

Holt  &  Co.,  New  York. 

Moulds,  Mildews,  and  Mushrooms.      Henry  Holt    & 

Co.,  New  York. 

There  should  also  be  a  good  collection  of  separate  publi- 
cations on  special  topics.  The  habit  should  be  formed  of 
reading  the  text  discussions  upon  the  topics  presented  in 
the  laboratory.  It  will  often  be  found  necessary  to  com- 
pare descriptions  and  to  attempt  to  account  for  variations 
and  contradictions  in  the  statements  made,  since  in  many 
cases  the  material  observed  by  the  student  will  not  show 
the  same  things  as  did  that  upon  which  the  text  statement 
was  based.  It  will  be  found  advantageous  if  the  text  work 
is  upon  definite  topics  related  to  the  laboratory  work, 
rather  than  a  study  of  the  text  chapter  by  chapter  as  pre- 


INTRODUCTION.  13 

sented.    The  topical  study  stimulates  to  examination  of 
several  texts. 

Separate  publications  written  by  various  research  stu- 
dents upon  topics  considered  in  the  laboratory  are  most 
helpful  in  any  extended  study.  If,  after  having  studied 
some  particular  type  or  in  connection  with  the  study,  the 
student  may  have  access  to  the  published  results  of  some 
one  who  has  made  careful  and  exact  investigation  of  that 
topic,  he  will  be  prepared  to  appreciate  and  assimilate  the 
work  and  point  of  view  of  the  special  student.  Further- 
more, such  literature  will  bring  the  student  more  nearly 
to  the  sources  from  which  text  statements  are  constructed, 
and  will  give  him  a  broad  view  of  the  field  of  work  found 
in  the  study  of  botany. 

Many  of  these  special  publications  are  in  foreign  lan- 
guages, but  this  should  not  be  a  serious  obstacle  to  the 
best  students.  Any  one  who  expects  to  do  extended  work 
in  a  biological  science  will  soon  find  that  he  must  have  a 
reading  knowledge  of  at  least  German  and  French,  and 
should  begin  to  familiarize  himself  with  these  languages 
as  early  as  possible. 

Acquaintanceship  with  good  botanical  magazines  has 
numerous  advantages.  Much  information  upon  the 
topics  studied  is  obtained;  the  general  spirit  of  scientific 
workers  may  become  gradually  transferred  to  the  student 
as  from  month  to  month  he  associates  himself  with  the 
writings  of  these  men;  a  knowledge  of  who  the  men  are 
who  are  active  in  the  subject  is  desirable  and  is  to  be 
obtained  from  a  study  of  the  literature  of  the  subject. 

5.  Collection  and  preservation  of  material. — Although 
much  of  the  material  used  must  be  supplied  to  the  student, 


14  INTRODUCTION. 

it  is  important  that  he  should  know  its  home,  its  general 
characteristics,  and  the  treatment  the  material  has  re- 
ceived in  case  it  has  been  necessary  to  preserve  it  in  order 
to  have  it  in  good  condition  at  the  time  the  study  is  to  be 
made.  Usually  fresh  material  is  highly  desirable.  Some 
of  this  may  be  kept  growing  in  the  laboratory,  and  local 
greenhouses  will  often  supply  the  things  needed  when 
they  cannot  be  found  in  their  natural  haunts. 

The  suggestions  as  to  habitat  given  at  the  beginning  of 
the  outline  upon  each  topic  must  be  general,  and  definite 
knowledge  of  just  where  in  each  locality  certain  forms  are 
found  must  be  supplied  by  the  instructor  and  the  stu- 
dents' own  observations. 

When  it  is  found  necessary  to  preserve  specimens  for 
future  use  various  methods  are  available.  The  simpler 
forms  of  plants  may  be  preserved  entire  in  seventy  per 
cent  alcohol  or  two  to  five  per  cent  formalin.  Pieces  of 
more  complex  plants  may  be  preserved  in  the  same  way. 
Some  of  the  Algag  may  be  kept  fairly  well  by  drying  upon 
a  piece  of  mica,  it  being  necessary  only  to  moisten  the 
specimens  when  they  are  to  be  used,  or  by  use  of  the  gly- 
cerin method  they  may  be  made  into  permanent  prepara- 
tions ready  for  use  at  any  time.  Specimens  of  the  higher 
plants  that  have  ecological  value  may  be  made  into  her- 
barium mounts  by  use  of  a  simple  plant-press,  driers,  and 
mounting-paper.  Preservation  by  means  of  the  more 
elaborate  processes  of  killing,  use  of  different  grades  of 
alcohol,  imbedding,  etc.,  will  be  found  fully  described  in 
Chamberlain's  "Methods  in  Plant  Histology." 

6.  Independent  work. — Finally,  it  should  be  said  that 
the  greatest  benefits  will  result  from  the  study  as  outlined 


INTRODUCTION.  15 

if  the  student  does  as  much  of  it  as  he  can  unassisted. 
Although  at  times  less  ground  may  thus  be  covered  in  a 
given  period,  more  ability  to  do  scientific  work  is  developed. 
Through  this  means  the  results  have  the  very  great  value 
of  individuality,  rather  than  the  much  smaller  values  that 
come  through  the  constant  attempt  at  being  in  conformity 
with  detailed  suggestions  given  by  another. 


GREEN    SLIME. 

Pleurococcus  viridis. 

THALLOPHYTES;  ALG^J  CHLOROPHYCE^E. 

PRELIMINARY. 

THE  plant  selected  to  illustrate  the  simplest  phase  of 
plant  life  is  found  in  all  parts  of  the  United  States,  and 
even  throughout  the  world.  It  grows  upon  the  surface 
of  various  objects,  being  often  so  abundant  as  to  give 
them  a  conspicuous  green  color,  especially  the  north  side 
of  old  fences,  barns,  and  the  trunks  of  trees,  becoming 
more  noticeable  after  a  few  days  of  damp  weather.  There 
are  several  other  closely  related  forms  that  may  be  used. 
In  fact  almost  any  unicellular  green  plant  will  answer, 
but  this  is  the  one  most  easily  found.  Pieces  of  bark  or 
wood  bearing  Pleurococcus  plants  may  be  kept  dry  for 
use,  and  will  give  a  fresh  appearance  when  moistened 
with  water,  and  even  retain  vitality  for  a  year  or  two. 

This  plant  belongs  to  the  great  group  known  as 
Thallophytes,  a  group  that  is  divided  into  Algae  and 
Fungi.  The  Algae  are  characterized  by  the  presence  of  a 
green  coloring-matter  known  as  chlorophyll.  Upon  the 
basis  of  various  combinations  of  colors  made  by  chloro- 
phyll and  other  coloring  substances,  as  well  as  upon  eer- 
ie 


PLEUROCOCCUS   VIRIDIS.  17 

tain  other  distinctions,  the  Algae  are  further  subdivided. 
One  of  these  subdivisions  of  the  Algae  is  the  Chlorophyceae, 
to  which  Pleurococcus  belongs. 

To  complete  the  following  study  it  will  be  necessary  to 
have  pieces  of  wood  bearing  Pleurococcus;  iodin;  and 
alcohol. 

LABORATORY   WORK. 
GROSS  STRUCTURE. 

Taking  a  fresh  specimen,  observe : 

1.  The  color. 

2.  The  evenness  with  which  the  plant  overspreads  the  sup- 
porting surface. 

3.  By  using  the  scalpel  observe  that  the  plants  are  easily 
removed  from  the  surface  on  which  they  grow. 

4.  The  pulverulent  appearance,  as  if  dusted  or  sanded  upon 
the  surface. 

5.  The  appreciable  thickness  reached  in  some  spots,  causing 
it  to  separate  in  scales  in  a  dried  specimen. 

Place  a  piece  of  bark  with  the  Pleurococcus  in  a  small 
quantity  of  alcohol;  after  an  hour  or  more  notice: 

6.  The  color  imparted  to  the  alcohol  by  the  coloring-matter 
of  the  plant,  the  chlorophyll.1 

7.  Observe  the  plants  after  the  chlorophyll  has  been  removed. 

MINUTE   STRUCTURE. 
I.  NUTRITIVE  OR  VEGETATIVE  STRUCTURES. 
Mount,  and  under  low  power  observe: 

1.  The  dust-like  particles  into  which  it  separates. 

2.  The  various  sizes  of  the  particles. 

1  Some  less  common  forms  of  unicellular  Algae,  as  well  as  many  more 
complex  ones,  are  red  or  purple  from  additional  coloring-matter. 


1 8  GREEN  SLIME. 

Under  high  power  notice: 

3.  The  individual  cells;  either  single  or  associated  in  groups. 

4.  The  size  of  the  cells;    some  small,  some  several  times 
larger.     By  means  of  a  stage  micrometer  determine  the 
actual  size  of  a  few  of  the  cells. 

5.  The  shape;  when  free,  and  when  in  groups. 

6.  The  cell  contents;    more  or  less  granular,  and  always 
green  from  the  presence  of  chlorophyll. 

7.  The  colorless  cell-watt  surrounding  each  cell. 

Press  upon  the  cover-glass  with  a  back-and-forth  movement 
and  the  walls  of  many  of  the  cells  and  cell  families  will  be 
ruptured  and  their  contents  ejected,  when  the  wall  can  be 
studied  easily. 

Stain  a  fresh  specimen  with  iodin,  and  observe: 

8.  The  brownish-yellow  color  given  the  contents  of  the  cell, 
showing  the  presence  of  protoplasm. 

9.  The  separate  chlorophyll  bodies,1  or  chloroplasts. 

10.  The  nucleus. 

11.  REPRODUCTION. 

1.  The  cell  multiplication,  or  vegetative  reproduction.     Ex- 
amine various  specimens  and  trace  the  successive  stages 
in  the  division  of  a  single  cell  to  form  a  cell  group. 

2.  Illustrate  the  various  structures,  and  also  method  of  repro- 
duction, by  drawings. 

ANNOTATIONS. 

Pleurococcus  is  a  unicellular  plant,  for  each  cell  performs 
individually  the  various  functions  pertaining  to  plant  life; 
and  this  is  true  whether  the  cells  do  not  separate  after 
division  or  remain  adherent  in  small  colonies. 

1  If  the  cells  are  properly  stained,  they  will  usually  remain  green, 
but  of  a  brighter  and  more  bluish  hue. 


PLEUROCOCCUS   VIRIDIS.  19 

The  essential  part  of  the  cell  is  the  protoplasm,  a  color- 
less semi-fluid  substance,  which  in  this  instance  is  obscured 
by  the  green  chlorophyll.  It  is  the  only  really  living 
active  agent  in  this  as  well  as  in  all  other  plants.  Its 
presence  here  is  made  manifest  by  the  yellowish-brown 
color  given  by  iodin. 

The  nucleus  is  a  special  organ  of  the  protoplasm  to  be 
seen  in  most  plant  cells.  It  is  definitely  related  to  the 
life  of  the  cell,  and  is  an  important  agent  in  the  process 
of  forming  new  cells.1  Chloroplasts  are  protoplasmic 
bodies  that  hold  the  green  pigment  chlorophyll.  The 
protoplasm  by  the  aid  of  the  chlorophyll  is  able  to  pro- 
duce, from  the  simple  inorganic  substances  carbon  dioxid 
and  water,  certain  complex  foods  such  as  starches  and 
sugars,  a  function  wanting  in  all  animals,  and  also  want- 
ing in  many  plants,  e.g.  Fungi  and  certain  colorless 
parasites  that  are  not  Fungi. 

The  solid,  firm,  and  nearly  colorless  cell-wall,  consist- 
ing essentially  of  cellulose,  is  a  product  of  the  protoplasm, 
and  serves  as  a  protection  to  it.  The  fine  granules  seen 
in  the  protoplasm  are  largely  food  materials  produced  by 
the  cell. 

The  multiplication  of  the  plant  by  cell-division  is  a 
very  common  method  throughout  the  vegetable  kingdom. 
The  nucleus  first  divides,  thus  forming  two  new  nuclei.2 
The  proptolasm  then  divides,  a  nucleus  remaining  in 
each  part,  and  a  wall  is  formed  between.  The  two  cells 
thus  produced  soon  attain  the  size  of  the  original  cell, 

1  These  structures  are  not  always  made  clear  by  iodin.     Chloriodid 
of  zinc  serves  well  to  demonstrate  them. 

2  Read  on  "nuclear  divisions"  in  reference  texts. 


20  GREEN  SLIME. 

when  they  in  turn  divide  into  two,  but  usually  by  a  par- 
tition at  right  angles  to  the  last  one,  and  so  on.  The  cells 
thus  formed  either  soon  become  separated,  or  remain 
mechanically  united. 

Another  method  of  establishing  new  plants  is  by  the 
production  of  zoospores.  The  protoplasm,  either  as  a 
whole  or  divided  into  several  parts,  escapes  from  the  cell- 
wall.  Each  mass  pushes  out  a  pair  of  delicate  filaments 
or  cilia,  which,  moving  rapidly  back  and  forth,  propel  the 
naked  protoplasm  through  the  water.  The  motion  and 
form  being  animal-like  suggested  the  name.  After  a 
period  of  activity  the  zoospores  come  to  rest,  draw  in  or 
drop  off  the  cilia,  secrete  a  cell- wall,  and  become  ordinary 
non-motile  Pleurococcus  cells.  In  some  plants  the  proto- 
plasm does  not  escape  from  the  cell-wall,  but  contracts 
somewhat,  cilia  are  protruded  through  openings  in  the 
wall,  and  the  cell  or  colony  is  propelled  about.  The  pro- 
duction of  zoospores  at  a  specified  time,  as  for  a  class 
demonstration,  is  attended  with  so  much  uncertainty  that 
their  study  has  been  omitted  from  the  laboratory  work. 
This  method  of  asexual  multiplication  will  be  studied  later 
under  more  favorable  conditions  in  other  plants. 


NOSTOC. 

THALLOPHYTES;  ALG^J  CYANOPHYCE.E. 

PRELIMINARY. 

Nostoc  may  usually  be  recognized  by  means  of  the 
dirty  bluish-  or  blackish-green  jelly-like  masses  occurring 
on  damp  earth,  or  on  water  plants,  or  in  free  roundish 
lumps,  either  floating  or  submerged  in  stagnant  water. 
During  periods  of  greater  dryness  the  jelly-like  masses 
frequently  form  rather  dry  and  flake-like  coatings  on  the 
earth  at  the  bottom  of  pools  that  are  becoming  dry.  Other 
members  of  the  Cyanophyceae,  the  group  of  Algae  to  which 
Nostoc  belongs,  are  often  found  in  bluish-green  jelly-like 
balls  and  bear  considerable  resemblance  to  the  Nostoc 
masses.  Such  forms  are  Glceocapsa,  Cylindrospermum, 
Clatherocystis,  Glceotrichia,  and  Rivularia. 

LABORATORY    WORK. 
GROSS  STRUCTURE. 

1.  Examine  one  of  the  colonies,  observing: 

a.  Color,  as  seen  in  reflected  and  in  transmitted  light. 

b.  The  jelly  which  encloses  the  plants. 

2.  Sketch  one  of  the  masses. 

21 


22  NOSTOC. 

MINUTE   STRUCTURE. 

1.  Mount  a  small  piece  of  the  colony,  and  under  low  power 
observe  the  almost  colorless  granular  jelly  in  which  are 
seen  chains  of  cells. 

2.  Note  whether  there  is  any  regularity  in  the  arrangement 
of  the  filaments. 

3.  Under  high  power  study  a  filament  to  determine: 

a.  The  form  and  number  of  cells  which  compose  it. 

b.  The  attachment  of  the  cells  one  to  another. 

c.  The  form,  position,  and  number  of  peculiar  enlarged 
cells,  the  heterocysts. 

d.  The  relation  of  the  heterocyst  to  reproduction  of  the 
filaments. 

e.  The  structure  of  a  single  cell. 

4.  Compare  several  plants  with  reference  to  the  points  sug- 
gested in  3. 

5.  Draw  in  detail  one  or  two  representative  filaments. 

ANNOTATIONS. 

The  individual  cell  of  a  Nostoc  plant  is  oblong,  has  a 
distinct  cell-wall  and  granular  bluish-green  protoplasm. 
Nuclei  are  not  easily  demonstrated,  and  until  recently 
their  existence  had  been  questioned.  Each  cell  is  proba- 
bly independent  of  its  neighbors  in  nutritive  work,  though 
doubtless  association  with  them  assists  it.  It  seems 
probable  that  Nostoc  plants  absorb  some  food  (organic 
matter)  from  the  water  or  earth,  for  they  grow  only  in 
situations  where  this  is  present.  This  would  remove 
the  necessity  of  so  much  food- making  by  these  plants, 
and  would  accord  with  the  small  amount  of  chlorophyll  in 
the  cells. 

While  in  Pleurococcus  each  plant  consists  of  a  single 


NOSTOC.  23 

cell,  in  Nostoc  many  cells  are  held  together  in  a  row 
partly  by  the  unbroken  portions  of  their  cell-walls  and 
partly  by  the  gelatinous  material  that  envelops  them. 
The  jelly  is  formed  by  a  chemical  alteration  of  the  outer 
parts  of  the  cell- walls.  They  thus  constitute  a  colony. 
In  Pleurococcus,  colonies  were  developed  when  a  number 
of  plants  had  formed  from  the  division  of  one  individual 
and  the  resulting  groups  had  not  been  disturbed;  but 
in  Nostoc  division  occurs  in  parallel  planes  only,  the 
cells  remain  long  united,  and  the  jelly  serves  to  hold 
and  protect  the  entire  colony. 

In  reproduction  Nostoc  differs  considerably  from  the 
unicellular  Algae.  The  division  of  any  of  the  cells  in 
the  chain  results  in  the  growth  of  the  filament,  and  not 
directly  in  the  production  of  a  new  chain.  Finally, 
when  this  chain  has  become  large,  heterocysts  are  formed 
from  certain  cells,  and  through  their  agency  the  filament 
is  broken  into  two  or  more  parts,  each  of  which  moves 
independently  and  may  even  creep  out  of  the  jelly  and 
start  a  new  colony.  Even  should  one  cell  be  cut  off 
from  all  others,  in  favorable  conditions  it  might  pro- 
duce a  new  filament  by  successive  divisions  and  may 
reproduce  itself  in  the  normal  way. 

This  plant  belongs  to  a  group  of  Algae  known  as 
Cyanophyceae.  The  group  is  characterized  by  the 
presence  of  phycocyanin,  a  blue  coloring-matter,  which 
together  with  chlorophyll  gives  the  bluish-green  color. 
The  plants  in  the  Cyanophyceae  are  all  quite  simple, 
few  being  more  complex  than  Nostoc,  and  some  even 
simpler. 


DARK-GREEN    SCUM. 

Oscillatoria. 

THALLOPHYTES;  ALG^J  CYANOPHYCE^. 

PRELIMINARY. 

THE  color  of  Oscillatoria,  almost  any  species  of  which 
may  be  used,  is  generally  sufficient  to  enable  one  to 
distinguish  it  at  sight.  Its  dark  blue-green  cast,  like 
that  of  Nostoc,  is  in  marked  contrast  with  the  yellow- 
green  of  most  other  plants  which  form  scums.  It  is 
very  common  on  stagnant  water,  often  forming  patches 
of  scum  thirty  centimeters  or  more  in  diameter,  which, 
becoming  loaded  with  dust,  finally  sink  to  the  bottom. 
It  is  also  very  common  about  watering- troughs,  along 
street  gutters,  at  the  outlet  of  drains,  on  wet  rocks,  giving 
them  a  slippery  surface,  on  the  earth  of  undisturbed 
pots  in  the  greenhouse,  and  in  all  localities  in  which 
the  water  contains  a  small  amount  of  decaying  organic 
matter.  It  can  usually  be  grown  indefinitely  in  an 
open  jar,  by  supplying  water  as  it  evaporates,  or  with 
less  trouble,  when  once  established,  in  an  unstoppered 
bottle,  in  which  a  small  twig  or  flower-stem  is  inserted 
to  provide  nutriment.  The  plants  are  often  to  be  found 
in  winter  in  as  good  condition  as  in  summer. 
24 


OSCILLATORIA.  25 

LABORATORY    WORK. 
GROSS  STRUCTURE. 

1.  Examine  a  small  mass  of  the  living  plant  that  has  been 
allowed  to  remain  undisturbed  for  several  hours  in  a 
watch-glass  of  water.     Observe: 

a.  The  deep  blue-green  color. 

b.  The  hair-like  unbranched  filaments,  radiating  from  the 
central  mass. 

2.  Sketch  the  plants  as  they  appear  in  the  watch-glass. 
Pulverize  a  mass  of  the  plant  that  has  been  thoroughly 

dried,  place  in  a  test-tube  or  vial  with  nearly  twice  the  bulk 
of  water,  and  after  ten  to  twenty-four  hours  observe: 

3.  The  color  of  the  solution  when  seen  by  transmitted  light, 
and  the  very  different  color  by  reflected  light. 

Pour  off  the  supernatant  water,  add  the  same  amount  of 
alcohol,  and  after  an  hour  or  more  observe: 

4.  The  yellow-green  color  imparted  by  the  chlorophyll. 

MINUTE  STRUCTURE. 

I.  GENERAL  CHARACTERISTICS. 
Under  low  power  observe: 

1.  The  color. 

2.  The  numerous  filaments  of  uniform  diameter,  destitute  of 
branches. 

3.  Study  the  movements. 

II.  THE  INDIVIDUAL  FILAMENT. 
Under  high  power  observe: 

i.  The  structure  in  detail,  as  follows: 

a.  The  rounded  extremities  of  uninjured  filaments. 

b.  The  outline  of  an  uninjured  apex,  whether  attenuated 
or  not,  and  whether  bent  to  one  side  or  straight. 


26  DARK-GREEN  SCUM. 

c.  The  partition-walls,  which  in  optical  section  are  seen  as 
delicate  lines  crossing  the  filament  and  dividing  it  into 
very  small  cells. 

d.  The  comparative  length  and  breadth  of  the  cells. 

e.  The  granular  contents,  and  their  distribution  in  the 

cell.1 

/.  The  delicate  colorless  sheath  to  be  seen  extending  beyond 
the  green  cells  at  some  torn  end  of  a  filament,  and  on 
which  sometimes  may  be  detected  transverse  lines  indi- 
cating the  position  of  the  end  walls  of  the  cells. 

2.  Theiurgidity  of  the  cells:  notice  that 

a.  The  transverse  walls  in  an  uninjured  filament  are  plane, 
while 

b.  The  last  cells  of  an  injured  filament  are  bulged  outward, 
making  the  outer  transverse  walls  convex,  the  pressure 
from  within  not  being  counterbalanced  from  without. 

3.  Draw  parts  of  two  or  more  plants. 

ANNOTATIONS. 

If  the  structure  of  Oscillatoria  be  carefully  compared 
with  that  of  Pleurococcus  and  Nostoc  more  points  of 
resemblance  will  be  found  than  appear  at  first  sight. 
New  cells  are  formed  by  the  process  of  division,  as  in 
Pleurococcus  and  Nostoc,  but  the  partition-walls  are 
always  parallel  and  in  one  direction,  which  disposes  the 
cell  families  in  filaments.  The  individual  cells  have 
thin  partition-walls,  the  office  of  protection  being  rele- 
gated to  the  sheath.  The  sheath,  which  is  formed  from 
the  outside  walls  of  the  cells  by  a  modification  of  the 
outer  portion,  is  a  structure  that  is  mostly  confined  to 
certain  groups  of  the  lower  plants,  although  it  has  some 

1  In  some  species  the  granules  are  collected  along  the  partition-walls. 


OSCILLATORIA.  27 

analogies  with  the  cuticle  of  the  higher  plants.  The  chlo- 
rophyll is  evenly  distributed  throughout  the  protoplasm. 
The  study  of  the  protoplasm  and  chlorophyll  is  much 
obscured  by  the  presence  of  the  peculiar  coloring-matter, 
phycocyanin,  characteristic  of  all  the  Cyanophyceae. 
Phycocyanin  is  insoluble  in  alcohol,  but  soluble  in  water 
when  the  plants  are  dead;  while  chlorophyll  is  soluble 
in  alcohol,  but  not  in  water;  hence  from  dead  plants 
water  removes  the  phycocyanin,  and  alcohol  the 
chlorophyll.  This  blue  color  is  often  seen  on  the  sides 
of  vessels  in  which  Oscillatoria  has  remained  so  long  as 
to  die,  and  also  staining  the  herbarium  sheets  on  which 
specimens  have  been  dried. 

The  cells  are  kept  together  chiefly  by  the  investing 
sheath,  into  which  they  are  packed.  This  structure, 
together  with  the  community  of  action  exhibited  in  pro- 
ducing the  peculiar  oscillating  and  nutating  movements, 
makes  it  evident  that  the  cells  of  each  filament  have  a 
certain  dependence  upon  one  another,  although  at  the 
same  time  each  is  capable  of  independent  existence. 
It  may  be  that  the  smallness  of  the  cells  and  the  thinness 
of  their  walls  is  in  some  way  correlated  with  this  unity 
of  function.  It  is  not  yet  definitely  known  how  the 
movements  in  Oscillatoria  are  produced. 

Turgidity  is  a  characteristic  of  living  cells.  It  is 
the  chief  means  by  which  the  soft  parts  of  plants  are 
enabled  to  keep  their  form,  and  otherwise  to  act  normally. 
It  is  brought  about  by  the  ability  of  the  protoplasm  to 
keep  certain  substances  from  escaping  through  it,  while 
their  presence  causes  water  to  pass  in  until  a  considerable 
internal  pressure  is  created. 


28  DARK-GREEN  SCUM. 

Pleurococcus,  Nostoc,  and  Oscillatoria  represent  forms 
of  simple  plant  life.  For  convenience  of  study  Pleurococ- 
cus has  been  placed  first ;  but  in  its  more  highly  organized 
nuclei  and  chlorophyll  bodies,  and  in  its  modes  of  repro- 
duction, it  shows  a  somewhat  higher  order  of  develop- 
ment than  Nostoc  and  Oscillatoria.  The  latter,  how- 
ever, in  the  arrangement  of  its  cells  offers  an  excellent 
introduction  to  the  higher  filamentous  forms,  to  be 
taken  up  next.1 

1  If  there  is  abundant  time,  it  will  be  found  advantageous  at  this 
point  to  take  up  a  study  of  other  representatives  of  the  Cyanophyceae 
and  unicellular  Chlorophycese.  Several  genera  of  Cyanophyceae  are 
suggested  in  connection  with  the  "Preliminary"  of  Nostoc  study,  p.  21. 


ULOTHRIX. 

THALLOPHYTES?  ALG^J  CHLOROPHYCEJE 

PRELIMINARY. 

SPECIES  of  Ulothrix  are  found  in  shallow  running 
water  either  in  streams  or  along  the  banks  of  larger 
bodies  of  water.  They  present  the  appearance  of  a 
bright  green  fuzzy  growth  upon  the  supports  on  which 
they  grow.1 

The  plants  may  be  distinguished  from  Cladophora, 
which  grows  in  similar  places,  by  being  more  slippery, 
shorter,  and  by  being  unbranched.  Even  with  these 
marks  it  is  not  always  easy  to  distinguish  some  members 
of  the  two  genera,  except  under  the  microscope.2 

When  good  material  is  found,  it  may  be  preserved  by 
the  ordinary  preservatives,  or  may  be  kept  by  drying 
upon  the  stones  or  sticks  to  which  it  has  grown.  This 
dried  material  may  be  made  ready  for  use  by  placing 
it  in  water  for  a  few  hours  or  a  day  before  it  is  to  be 
used.  Such  material  usually  forms  reproductive  bodies 

1  Occasionally  Ulothrix  plants  are  found  floating  in  free  water. 

3  In  some  places  it  may  be  impossible  to  locate  specimens  of  this 
plant.  When  such  is  the  case,  preserved  material  may  be  had  from 
a  supply  house.  The  form  is  of  especial  importance,  but  if  it  cannot 
be  obtained,  some  of  the  features  may  be  illustrated  by  the  plant  Cla- 
dophora. 

29 


30  ULOTHRIX. 

soon  after  being  placed  in  water.  Fresh  material  may 
usually  be  made  to  reproduce  itself  by  keeping  it  in  a 
shallow  dish  and  placing  the  dish  in  the  dark.  Main- 
taining an  even  temperature  and  slowly  increasing  the 
density  of  the  liquid  tends  to  induce  zoospore  formation 
in  this  as  well  as  several  other  Algae.  Reproductive 
bodies  when  fonned  in  such  places  are  set  free  after  the 
material  has  been  in  the  light  for  an  hour  or  two. 

LABORATORY  WORK. 

GROSS  STRUCTURE. 

Carefully  remove  some  of  the  plants  from  their  support  and 
observe  how  firmly  they  are  attached.  Place  a  small  mass  in 
a  watch-glass,  and  observe: 

1 .  The  color  as  compared  with  that  of  the  other  plants  studied. 

2.  Whether  plants  are  enclosed  in  jelly. 

3.  The  feel  of  the  mass. 

4.  The  approximate  length  of  single  filaments. 

MINUTE   STRUCTURE. 

I.  THE  NUTRITIVE  PLANT  BODY. 

With  a  few  plants  mounted  on  a  slide,  under  the  low  power 
note: 

1.  The  size  and  form  of  the  cells. 

2.  Whether  they  are  held  together  as  in  Nostoc  and  Oscillatoria. 

3.  Any  peculiarities  of  the  basal  and  apical  cells.1 
With  the  high  power  observe: 

4.  The  form  and  position  of  the  plastid  in  each  cell. 

5.  Whether  the  basal  " holdfast"  contains  a  chloroplast.2 

1  If  the  ends  are  found  to  consist  of  broken  cells,  search  for  sound 
specimens. 

2  In  most  cases  the  "holdfast"  is  injured  in  obtaining  the  material, 
consequently  it  may  be  impossible  to  find  a  good  specimen. 


ULOTHRIX.  3 1 

6.  Stain  a  few  plants  with  a  solution  of  iodin  and  try  to  find 
the  nucleus.     In  case  the  chloroplast  should  contain  starch 
it  will  usually  be  stained  a  dark  blue  by  the  iodin.    The 
cytoplasm  may  also  be  stained  and  made  more  easily  seen 
by  this  process. 

7.  Draw  a  few  cells  showing  details  of  structure.    Also  draw 
the  "holdfast,"  in  case  one  is  found. 

II.  REPRODUCTION. 

A.  VEGETATIVE. 

In  connection  with  the  processes  of  growth  the  cells  divide, 
thereby  increasing  the  length  of  the  plant.  Watch  for  evi- 
dence as  to  whether  these  elongated  plants  may  break,  thus 
forming  two  or  more  plants. 

B.  BY  SPORES.* 

Locate  some  cells  in  which  the  protoplasm  has  been  divided 
into  four  or  more  zoos  pores,  and  study  the  spores,  noting: 

1.  Their  form. 

2.  The  cilia  at  the  smaller  end.     How  many? 

3.  The  plastid  within  the  spore. 

4.  How  the  zoospores  escape  from  the  cell  in  which  they  are 
formed. 

5.  Try  to  find  some  of  the  zoospore-like  bodies  that  are 
uniting  in  pairs  thus  forming  sexual  spores. 

In  a  dish  of  material  which  has  been  standing  for  some 
days  will  usually  be  seen  a  ring  of  young  plants  adhering  to  the 
glass  at  the  surface  of  the  water.  Remove  and  mount  some 
of  this  material  Observe : 

6.  Spores  just  beginning  to  germinate. 

1  Outline  is  not  provided  for  studying  all  of  the  details  of  reproduc- 
tion in  Ulothrix  as  those  details  are  given  in  current  text-books,  since 
investigations  now  being  made  at  the  University  of  Chicago  indicate 
that  the  text-book  accounts  are  in  error. 


32  ULOTHRIX. 

7.  Young  plants  of  several  cells  beginning  to  assume  the 
characteristics  of  their  parents. 

8 .  The  developing  ' '  holdfast . ' ' 

Make  drawings  illustrating  the  stages  seen  in  the  process 
of  reproduction. 

ANNOTATIONS. 

In  the  plant  Ulothrix  we  have  our  first  illustration 
of  a  filamentous  green  Alga  of  the  family  Chlorophyceae. 
Its  cylindrical  cells  are  placed  end  to  end,  and  much 
more  firmly  united  than  those  of  any  plant  we  have  yet 
studied.  Furthermore,  in  most  species  the  basal  cell 
attaches  the  plant,  thereby  giving  it  a  degree  of  perma- 
nence of  location.  In  each  cell,  excepting  the  "hold- 
fast," we  have  a  well-organized  chloroplast  in  which 
are  special  nutritive  organs  known  as  pyrenoids,  which 
are  peculiar  to  some  Algae.  The  plants  grow  in  length 
by  having  the  cells  enlarge  and  divide  at  right  angles 
to  the  long  axis  of  the  filament.  Sometimes  plants 
break,  resulting  in  the  production  of  two  or  more  new 
individuals. 

Asexual  reproduction  takes  place  through  the  formation, 
by  internal  division,  of  specialized  bodies  known  as  spores, 
called  zoospores  because  they  move  as  certain  small 
animals.  These  zoospores  may  be  formed  in  the  interior 
of  any  nutritive  cell  by  the  division  of  its  protoplasm, 
all  of  which  is  used  in  their  formation.  When  the  wall 
of  the  mother- cell  breaks,  the  zoospores  escape  and  swim 
about  for  a  time,  then  come  to  rest  on  some  support, 
attach  themselves  at  their  ciliated  end,  and  begin  to  grow 
into  new  Ulothrix  plants.  Obviously  this  zoospore  habit 


ULOTHRIX.  33 

gives  the  plant  advantage  over  the  plants  heretofore  con- 
sidered, because  it  provides  for  more  certain  and  rapid 
multiplication  and  wider  distribution. 

Sometimes  bodies  like  zoospores,  but  not  true  spores 
at  all,  since  they  do  not  reproduce  the  kind  of  plant  that 
formed  them,  unite,  thus  forming  a  spore.  When  two  of 
these  bodies  unite  (whence  called  gametes]  they  form  a  spore 
which  can  reproduce  the  kind  of  plant  that  formed  them. 
Such  a  spore  is  sexual  since  it  is  formed  by  the  union 
of  cells,  and  this  one  being  formed  by  the  conjugation 
(yoking  together)  of  similar  gametes  is  called  a  zygospore 
(to  yoke;  spore).  Observe  that  gametes  from  widely 
separate  individuals  may  unite,  thus  bringing  into  the 
sexual  spore  protoplasm  widely  separated  in  origin. 
It  is  evident  that  reproduction  by  zoospores  involves  no 
opportunity  of  introducing  new  vigor  from  a  second  plant 
as  does  reproduction  by  sexual  spores.  But  it  must  be 
kept  in  mind  that  sexuality  in  plants  originated  from 
the  non-sexual  processes  of  zoospore  formation,  and  that 
zoospores  are  the  cells  that  begin  to  function  as  gametes. 
From  the  condition  illustrated  by  Ulothrix  there  begins  a 
highly  important  series  of  differentiations  of  gametes 
looking  toward  the  formation  of  the  sexual  spore. 


CLADOPHORA. 

THALLOPHYTES;  ALG2E;  CHLOROPHYCE.E. 

PRELIMINARY. 

THERE  are  many  species  of  this  plant,  almost  any  of 
which  will  be  found  suitable  for  laboratory  work.  Most 
of  the  species  grow  attached  to  some  support  in  moving 
water,  while  a  few  may  be  found  floating  upon  the  sur- 
face. The  plants  are  much  coarser  than  Ulothrix  and 
also  much  branched,  so  that  they  may  be  distinguished 
fairly  well  by  the  eye  alone.  They  grow  well  at 
almost  all  times  of  the  year.  A  week  or  more  before 
the  study  is  to  be  made  some  vigorously  growing  plants 
should  be  placed  in  a  dish  of  water,  in  a  rather  dark 
place,  where  there  is  a  fairly  constant  favorable  tempera- 
ture. The  water  in  the  dish  should  be  allowed  to  evap  • 
orate  slowly.  This  procedure  will  often  cause  some  of  the 
cells  to  produce  spores  in  a  favorable  condition  for  study.1 

1  If  satisfactory  material  was  at  hand  in  the  study  of  Ulothrix,  the  re- 
production of  Cladophora  may  well  be  omitted  since  it  is  quite  similar 
to  that  of  Ulothrix. 

34 


CLADOPHORA.  3$ 


LABORATORY    WORK. 

GROSS  STRUCTURE. 

1.  With  some  plants  in  a  dish  of  water  compare  with  Ulothrix 
as  to  color,  coarseness,  and  position  in  the  water. 

2.  By  lifting  some  plants  from  the  water  on  a  piece  of  white 
paper,  determine  whether  the  diameter  of  a  filament  is 
the  same  throughout. 

3.  Examine  the  sides  of  a  dish  of  plants  which  has  been  in 
the  laboratory  a  week  or  more  to  see  if  any  of  the  germi- 
nating spores  are  beginning  to  attach  themselves  to  the 
dish. 

MINUTE  STRUCTURE. 

I.  THE  PLANT  BODY. 

Mount  one  or  two  plants  and  under  low  power  observe: 

1.  The  form. 

2.  The  relative  size  of  segments  1  from  base  to  tip. 

3.  The  form  of  segments  at  tips  of  branches  as  compared  with 
those  lower  down. 

4.  The  points  at  which  branches  arise. 

5.  Sketch  a  small  plant  or  part  of  a  large  one. 

II.  THE  SEGMENT. 

Under  high  power  observe: 

1.  The  wall  of  a  single  segment  of  the  plant  enclosing: 

2.  The  protoplasm,  of  which  (a)  cytoplasm,  (b)  definitely 
organized  chloroplasts,  and  (c)  a  few  pyrenoids  may  be 
distinguished. 

1  In  Cladophora  each  apparent  cell  is  really  a  complex  structure 
within  one  cellulose  wall.  Such  a  segment  is  said  to  be  a  casnocyte. 
To  observe  all  the  points  suggested  it  will  be  necessary  to  have  specially 
stained  specimens. 


36  CLADOPHORA. 

3.  Whether  filaments  are  furnished  with  a  sheath. 

4.  How  a  new  branch  develops  from  a  coenocyte. 

5.  By  means  of  a  specially  stained  specimen  locate  the  numer- 
ous nuclei  to  be  found  in  one  coenocyte. 

6.  Draw  an  entire  segment  and  part  of  one  from  which  a  new 
branch  is  developing. 

III.  REPRODUCTION. 

1.  By  use  of  the  low  power  try  to  locate  coenocytes  in  which 
the  protoplasm  has  divided  into  a  large  number  of  small 
spores. 

2.  With  high  magnification  study  the  form  and  movement  of 
the  spores.   By  staining  with  iodin  it  is  sometimes  possible 
to  see  the  cilia  by  means  of  which  movement  occurs. 

3.  Study  some  spores  which  have  come  to  rest  on  the  sides 
of  the  dish  and  note  the  changes  as  they  are  beginning  to 
produce  new  individual  plants. 

4.  Try  to  determine  whether  any  of   these   ciliated  bodies 
unite  to  form  zygospores. 

5.  Make  drawings   illustrating   the    reproduction    of  Cla- 


ANNOTATIONS. 

The  vegetative  structure  of  Cladophora  is  more  com- 
plex than  that  of  any  other  plant  studied.  The 
divisions  usually  called  individual  cells  are  really  com- 
posed of  a  wall  enveloping  what  are  the  essential  parts 
of  many  cells.  The  nuclei  of  the  several  cells  held  in 
the  common  wall  may  be  seen  by  means  of  special  stains. 
These  segments  are  so  arranged  as  to  compose  a  very 
greatly  branched  plant,  which  because  of  this  branching 
is  enabled  to  expose  more  chlorophyll  to  the  light.  That 


CLADOPHORA.  37 

Cladophora  is  well  adapted  to  meet  its  problems  of 
living  is  indicated  by  the  almost  universal  presence 
of  the  pi  nt  wiierever  there  is  a  constant  water-supply. 
By  means  of  its  strong  "holdfast"  it  is  enabled  to  grow 
in  running  water  and  on  wave-beaten  rocks,  in  which 
places  it  frequently  forms  very  luxuriant  growths. 

In  reproduction  Cladophora  bears  close  resemblance 
to  Ulothrix. 


COMMON     POND-SCUM. 

Spirogyra. 

THALLOPHYTES;  ALG^J  CHLOROPHYCE.E. 

PRELIMINARY. 

THE  members  of  this  genus  are  abundant  in  stagnant 
water  everywhere,  forming  bright  yellow-green  scums  of 
great  extent,  sometime  diffused  beneath  the  surface,  or 
occasionally  in  running  water  attached  to  stones.  They 
may  be  distinguished  readily  from  all  other  scum-pro- 
ducing plants,  except  from  a  few  of  their  close  allies,  in 
having  a  slippery  feel,  and  being  composed  of  long 
unbranched  filaments,  which  string  out  like  wet  hair 
when  withdrawn  from  the  water.  The  allied  kinds, 
which  cannot  be  separated  by  this  test,  will  at  once  be 
distinguished  when  placed  under  the  microscope  by 
possessing  no  spiral  chlorophyll  bands  as  does  Spirogyra. 
When  growing  vigorously  the  masses  of  Spirogyra  are 
an  intense  light  green;  when  beginning  to  form  spores 
they  turn  yellowish,  and  look  very  uninviting;  but  as 
the  characteristics  which  distinguish  the  species  are 
largely  drawn  from  the  reproductive  condition,  the  col- 
lector soon  learns  to  regard  these  unsightly  objects  with 
favor. 

38 


SPIROGYRA.  39 

The  vegetative  condition  may  be  found  at  any  time 
during  the  warmer  portion  of  the  year.  The  reproduc- 
tive condition  occurs  from  early  spring  to  June  and 
July,  and  sparingly  during  the  remainder  of  the  warm 
season.  The  species  usually  grow  intermixed,  and 
almost  any  species  gathered  will  answer  for  the  present 
study,  though  one  with  a  small  number  of  loose  spirals 
is  best. 

LABORATORY  WORK. 

GROSS  STRUCTURE. 

Taking  fresh  specimens  in  a  white  dish,  observe: 

1.  The  vivid  but  yellow-green  color  as  seen  in  the  mass. 

2.  The  slippery  feel  when  the  plant  is  taken  between  the 
fingers. 

3.  The  fine  unbranched  filaments  of  which  it  is  composed. 

4.  The  uniform  diameter. 

5.  Their  length. 

Place  some  in  alcohol  and  after  some  time  notice: 

6.  The  color  imparted  to  the  alcohol  by  the  chlorophyll. 

MINUTE   STRUCTURES. 

I.  VEGETATIVE  CHARACTERS. 

Under  low  power  observe: 

1.  The  length;  if  traced  to  the  end,  the  filament  will  probably 
be  found  broken. 

2.  The  uniform  diameter. 

3.  The  cell  contents;  colorless,  except  the  conspicuous  green 
chlorophyll  bands. 

Using  a  high  power  observe: 

1.  The  shape  of  the  cells. 

2.  Their  relative  length  and  breadth. 


40  COMMON  POND-SCUM. 

3.  The  cell  wall: 

a.  The  lateral  walls;    parallel  and  without  markings  of 
any  sort. 

b.  The  end  walls;  at  right  angles  to  the  longitudinal  axis, 
and  plane  (unless  slightly  nodulated  or  infolded,  which 
occurs  in  a  few  species). 

4.  The  absence  of  any  visible  sheath,  although  the  presence 
of  at  least  a  thin  one  has  been  demonstrated  by  the  slip- 
pery feel. 

5.  The  cell  contents: 

a.  The  chlorophyll  bands  (chloroplasts) ,  taking  a  spiral 
course  from  one  end  of  the  cell  to  the  other,  passing 
near  the  periphery.  Note: 

(1)  The  number  in  each  cell.1 

(2)  The  number  of  turns  of  the  spiral. 

(3)  The  surface,  the  crenulated  and  wrinkled  margin, 
and  the  turned-up  edges  of   the  band  forming  a 
more  or  less  flattened  V  in  optical  section.     To  ob- 
tain a  complete  conception  of  these  particulars,  first 
focus  upon  the  peripheral  surface  of  the  band,  i.e. 
upon  the  upper  (outer)  surface  of  the  part  nearest 
the  eye,  then  focus  upon  the  axial  (inner)  surface, 
and  finally  examine  the  profile  of  the  band  seen  on 
the  right  or  left  of  the  cell. 

(4)  The  nodules  at  varying  distances  along  the  median 
line  of   the  band.      Stain  with  iodin,  and  in  the 
nodule  note: 

(a)  An  outer  ring  of  granular  material  which  is  more 
deeply  colored,  the  starch  grains,2  and 

(b)  A  central  light  spot,  pyrenoid.     Both  are  best 
seen  when  but  faintly  colored. 

1  If  crowded  so  as  to  make  a  direct  count  difficult,  see  Bot.  Gaz.  9:  13, 
for  an  easy  method  of  determining  the  number. 

*  Unless  the  plants  have  been  in  sunlight  for  a  few  hours  the  test 
for  starch  may  not  be  fully  successful. 


SPIROGYRA.  41 

(5)  The  yellowish-brown  color  finally  imparted  to  the 
chlorophyll  band. 

b.  The  feeble  brownish  color  given  to  the  remainder  of  the 
contents  of  the  cells,  deeper  along  the  periphery. 

c.  In  cells  presenting  the  least  obstruction  from  the  chloro- 
phyll bands    search  for  a  colorless  oval  or  spindle- 
shaped  body,  the  nucleus,1  imbedded  near  the  center  of 
the  cell  in  a  mass  of  protoplasm  with  arms  radiating  to 
the  peripheral  protoplasm.     The  peculiar   conditions 
found  here  would  at  first  glance  lead  one  to  suppose 
the  real  nucleus  to  be  a  nucleolus. 

II.  REPRODUCTIVE  CHARACTERS. 

Mount  fi  aments  thought  to  be  in  reproductive  stage,  and 
under  low  power  search  for: 

1.  Filaments  lying  side  by  side  in  pairs,  held  together  by 
transverse  branches,  the  conjugating  tubes. 

2.  Some  filaments  having  an  irregular  outline,  caused  by 
uneven  lateral  expansions,  the  beginning  of  conjugating 
tubes.     When  conjugating  filaments  are  found,  observe: 

3.  The  varying  character  of  the  contents  of  the  cells:   some 
with  spiral  bands  of  chlorophyll;    some  with  a  confused 
green  mass;   some  with  green  or  brown  oval  bodies,  the 
zygospores;   some  empty. 

Under  high  power  observe : 

4.  The  conjugating  tube  connecting  two  cells: 

a.  The  enlargement  at  the  middle,  where  an  indentation 
marks  the  line  of  union  of  the  two  originally  separate 
branches. 

b.  What  variations  in  directions  of  the  conjugating  tubes 
can  be  found  ? 

1  This  is  not  easily  demonstrated  in  all  species,  although  the  iodin 
usually  stains  it  a  light  brownish  color. 


42  COMMON  POND-SCUM. 

c.  Search  for  various  stages  in  the  growth  of  the  conju- 
gating tubes,  and  observe  whether  tubes  from  con- 
jugating cells  always  begin  in  pairs;  also  whether  one 
cell  ever  conjugates  with  more  than  one  other  cell. 

5.  The  cell  contents. 

a.  By  studying  various  specimens,  trace  the  changes  from 
the  vegetative  condition  through  the  several  stages  of 
disintegration  of  the  chlorophyll  band  and  contraction 
of  the  protoplasm  to  the  formation  of  a  rounded  green- 
ish-brown mass;    noticing  at  the  same  time  that  this 
change  is  contemporaneous  with  the  formation  of  the 
conjugating  tube.     Usually  all  stages  are  easily  found. 

b.  Where  the  conjugating  tube  is  fully  formed,  note  that 
one  cell  is  empty,  and  the  connected  cell  contains  a 
single  mass,  the  spore  produced  by  the  conjugation. 

c.  When  the  cells  of  two  filaments  have  conjugated  see 
whether  all  the  zygospores  formed  lie  in  the  cells  of  one 
filament  of  the  pair. 

6.  The  mature  zygospore.    Note: 

a.  Shape  and  color. 

b.  Contents. 

c.  The  wall  of  greater  or  less  thickness,  usually  resolvable 
into  two  or  more  layers  of  different  colors. 

7.  Make  drawings  to  illustrate  the  parts  and  changes  of  the 
reproductive  filaments. 

ANNOTATIONS. 

In  form  and  manner  of  growth  Spirogyra  shows  no 
essential  features  not  seen  in  plants  already  studied, 
except  the  arrangement  of  the  protoplasm  and  chlorophyll 
bodies.  The  filaments  are  built  on  the  plan  of  Oscillatoria 
and  Ulothrix,  with  the  cells  larger,  and  the  sheath  so 
much  reduced  that  it  can  be  demonstrated  only  with 


SPIROGYRA.  43 

difficulty.  In  some  species  of  the  closely  related  genus 
Zygnema,  however,  the  sheath  is  readily  discernible. 
The  increase  in  the  number  of  cells  is  effected  in  the 
same  manner  as  in  the  other  filamentous  plants,  i.e. 
by  the  division  of  the  cell  into  halves  by  a  transverse 
partition  always  in  the  same  plane,  with  subsequent  ex- 
pansion of  the  new  cells. 

The  distribution  of  the  protoplasm  here  as  in 
Cladophora  and  Ulothrix  shows  a  marked  advancement 
over  the  lower  plants.  Instead  of  being  diffused  evenly 
through  the  cell,  it  forms  a  layer  lining  the  cell-wall, 
while  it  only  partly  occupies  the  central  portion  of  the 
cell.  The  remaining  space  is  filled  by  the  cell-sap, 
which  consists  of  water  holding  various  substances  in 
solution.  Within  the  central  part  of  this  sap  region  is 
the  nucleus  suspended  by  means  of  cytoplasmic  threads 
from  the  peripheral  protoplasm.  In  the  form  of  the 
chloroplast  band  we  have  a  striking  feature;  for  although 
it  is  common  to  have  the  chlorophyll  held  in  well-defined 
bodies,  it  is  only  in  Spirogyra  and  its  close  relatives  that 
they  assume  such  peculiar  and  beautiful  shapes. 

The  presence  of  starch  granules  in  the  chlorophyll 
bodies  is  a  very  significant  fact  physiologically.  Starch- 
like  substances,  which  afterwards  may  be  made  into 
starch,  are  among  the  first  products  that  chemists  have 
been  able  to  determine  in  the  processes  of  making  food 
material  by  plants.1 

The  starch  is  imbedded  in  the  chloroplasts,  and  is 
quite  distinct  from  the  pyrenoid,  although  the  constancy 

1  Read  on  "Photosynthesis"  and  "Construction  of  Foods  by  Green 
Plants,"  sometimes  called  assimilation  in  various  texts  at  hand. 


44  COMMON  POND-SCUM. 

in  the  relative  position  of  the  two  would  indicate  some 
connecting  influence.  The  pyrenoids  have  been  long 
known  and  variously  interpreted,  but  recent  careful 
studies  show  that  their  outer  parts  are  converted  bodily 
into  starch.  Their  chemical  constitution  is  uncertain, 
though  they  respond  to  tests  for  proteids.  Their  occur- 
rence is  not  common  throughout  the  plant  kingdom. 

When  we  examine  the  reproduction  of  Spirogyra,  we 
find  that  in  its  details  it  is  quite  unlike  any  plant  yet 
studied.  In  it  we  have  the  sexual  process  much  more 
developed  than  in  Ulothrix,  inasmuch  as  the  sex-cells,  or 
gametes,  do  not  become  free- swimming  bodies,  but  by 
means  of  a  conjugating  tube  one  travels  directly  to  the 
other  and  unites  with  it  to  form  a  spore. 

That  these  fusing  cells  are  not  always  of  the  same 
size  is  sometimes  quite  clear,  and  it  has  often  been  pointed 
out  that  they  are  sometimes  unlike,  but  they  are  so 
essentially  similar  that  they  can  hardly  be  distinguished 
as  male  and  female  elements  in  spore  formation.  Hence 
the  reproduction  is  said  to  be  isogamous,  i.e.  by  similar 
gametes. 

The  zygospore  formed  thus,  after  developing  a  heavy 
protecting  wall,  may  pass  through  a  long  period  of  rest, 
and  then  by  germination  may  develop  a  new  plant. 
Evidently,  therefore,  Spirogyra  is  not  only  a  larger  and 
more  complex  plant,  and  thereby  able  to  do  more  work, 
but  has  developed  the  special  device  of  a  well-protected 
spore  which  is  adapted  to  carrying  the  plant  through 
drouth  and  winter.  Since  these  spores  are  dense  and 
have  a  heavy  wall  they  sink  to  the  bottom  of  the  water 
as  soon  as  they  are  set  free  by  the  partial  decay  of  the 


SP1ROGYRA.  45 

walls  of  the  filament  in  which  they  were  formed.  Although 
formed  in  the  earlier  part  of  the  warm  season,  usually 
they  will  not  germinate  at  once,  but  remain  dormant 
in  the  mud  at  the  bottom  of  the  pool  or  stream  until 
the  next  spring,  when  they  form  new  plants. 


VAUCHERIA    SESSILIS. 


THALLOPHYTES;          ALG^;         CHLOROPHYCE^. 

PRELIMINARY. 

THIS  species  of  Vaucheria  is  quite  common  on  the 
damp  earth  and  pots  of  greenhouses,  and  may  often  be 
found  out  of  doors  in  damp  shady  places.  Other  species 
may  also  be  found  in  similar  places  as  well  as  in  quiet 
pools  of  water.  The  members  of  the  genus  may  usually 
be  distinguished  by  their  coarseness,  the  filament  often 
being  large  enough  to  be  seen  singly  with  the  unaided 
eye.  When  growing  upon  damp  earth  the  slightly 
brownish-green  color  and  the  felt-like  appearance  make 
it  rather  easy  to  distinguish  this  plant  from  other  Algae. 
Material  in  the  reproductive  stage  is  not  always  found 
easily  in  nature,  and  when  found  should  be  preserved. 
It  may  be  obtained  by  placing  some  of  the  vegetative 
plants  in  a  dish  of  water  and  putting  them  where  they 
will  be  well  lighted.  In  this  way  zoospores  and  sexual 
spores  may  usually  be  obtained  in  from  five  to  ten  days. 
This  treatment  also  produces  new  growth  favorable  for  a 
study  of  vegetative  structures. 
46 


VAUCHERIA    SESSILIS.  47 


LABORATORY  WORK. 

GROSS  STRUCTURE. 

1.  Study  the  general  appearance  of  the  mat  of  plants  as  they 
rest  on  earth  or  in  water. 

2.  Note  whether  they  are  entirely  outside  the  earth. 

3.  Note  whether  the  growing  tips  have  any  definite  position 
relative  to  the  light. 

Float  out  some  of  the  plants  in  a  watch-glass,  and  by  use  of 
the  hand-lens  note: 

4.  Branching  of  plant  body. 

5.  Whether  any  small  dark  bodies — oogonia  in  which  oospores 
are  found — can  be  seen  at  the  sides  of  plants.     Even  when 
present  they  cannot  always  be  seen  with  the  hand-lens. 

6.  Whether   there   are   large,  free,  green,  swimming  spores, 
the  zoospores. 

MINUTE    STRUCTURE. 

I.  VEGETATIVE   CHARACTERS. 

Carefully  remove  the  earth  from  a  few  plants  and  mount. 
With  either  low  or  high  power,  as  the  case  may  require,  observe: 

1.  The  length,  diameter,  and  branching. 

2.  Absence  of  cross  cell-walls  separating  the  protoplasm  into 
the  ordinary  cells.     It  is  a  ccenocyte.     Examine  specially 
stained  specimens. 

3.  Position,  form,  and  abundance  of  chloroplasts. 

4.  Parts  of  some  plants  which  have  no  chloroplasts.     Ac- 
count for  their  absence. 

5.  The  method  of  formation  of  new  chloroplasts,  as  shown 
within  actively  growing  plant-tips. 

6.  Make  drawing  illustrating  the  structure  of  the  plant  body. 


48  VAUCHERIA    SESSILIS. 

II.  REPRODUCTIVE  CHARACTERS. 

1.  Asexual  reproduction. 

At  the  tips  of  some  branches  search  for  the  following  stages: 

a.  Where  there  has  been  formed  a  transverse  partition- 
wall. 

b.  Where    the   protoplasm   thus    enclosed    is    becoming 
spherical  in  form. 

c.  Where  this  large  mass  of  protoplasm,  which  is  a  com- 
pound zoospore,  is  escaping  from  its  enclosing  walls. 

d.  Search  for  free  zoospores  and  observe  the  movements. 
Around  the  margin  of  the  dish,  or  held  by  the  older  plants 

if  the  material  has  been  kept  for  a  few  days,  may  be  found 
specimens  which  when  mounted  will  show: 

e.  Young  plants  beginning  to  grow  from  zoospores. 
/.  Draw. 

2.  Sexual  Reproduction. 

On  the  side  of  filaments  may  frequently  be  seen  some 
branches  of  one  or  two  kinds,  as  follows: 

a.  The  oogonium,  an  oval  body  with  a  beak-like  tip,  con- 
taining an  oosphere,  the  female  gamete,  or  sex  spore, 
the  oospore. 

b.  Arising  from  the  filament  near  the  base  of  the  oogonium 
is  the  antheridium,1  an  elongated  and  coiled  body. 

c.  Note  how  the  structures  are  adapted  to  aid  in  the  union 
of  the  passive  egg  of  the  oogonium  and  the  motile  sperm 
from  the  antheridium. 

d.  Observe  the  very  heavy  wall  about  the  oospore  or  fer- 
tilized egg.     Of  what  significance  is  this? 

e.  Draw  oogonia,  antheridia,  and  oospores. 

1  In  V.  sessilis  the  antheridial  stalk  arises  as  a  separate  branch  from 
the  plant  body,  while  in  other  species,  e.g.  V.  geminata,  the  anther- 
idial stalk  is  the  termination  of  a  branch  on  the  side  of  which  one  or 
more  oogonia  may  be  borne. 


VAUCHERIA   SESSILIS.  49 

ANNOTATIONS. 

We  have  in  Vaucheria  a  green  Alga  which  is,  in  some 
ways,  quite  peculiar.  It  has  a  ccenocytic  plant  body; 
it  is  relatively  rather  large,  and  produces  massive  zoospores 
which  are  covered  with  cilia  and  are  of  immense  size 
when  compared  with  other  zoospores.  These  are  called 
compound  zoospores,  and  are  supposed  to  represent  many 
small  zoospores,  each  pair  of  cilia  protruding  through  a 
thin  peripheral  sheath  corresponding  to  the  pair  of  a 
simple  zoospore.  Furthermore,  the  plants  of  this  genus 
have  a  distinct  tendency  to  frequent  damp  earth  rather 
than  to  live  in  the  water. 

As  a  form  illustrating  the  line  of  evolution  of  sexual 
reproduction  in  the  Algae  Vaucheria  is  quite  significant. 
Here  the  gametes  are  not  similar,  as  in  Ulothrix  and 
Spirogyra,  one  having  become  large  and  inactive,  while 
the  other  is  small  and  active.  This  differentiation  is 
indicated  by  using^th^term  female  gamete,  or  egg>  for 
the  larger  gamete,  and  male  gamete,  6r  'ffym  or  aMhero- 
zoid,  for  the  smaller  one.  The  larger  size  of  the  ooapfcre, 
produced  by  union  of  the  sperm  with  the  egg,  makes 
possible  the  storage  of  greater  amounts  of  food  material 
for  the  nourishment  of  the  new  plant  when  it  germinates. 
Fertilization  is  accomplished  by  the  active  swimming 
of  the  sperm  to  the  egg  and  fusing  with  it.  Since  the 
number  of  sperms  is  very  much  greater  than  the  number 
of  eggs,  the  chances  of  fertilization  are  thereby  greatly 
increased. 

It  is  to  be  noted  further  that  ordinary  vegetative  cells 
do  not  produce  either  zoospores  or  gametes.  In  the 


$0  VAUCHERIA   SESSILIS. 

case  of  zoospores  the  end  of  a  nutritive  filament  is  made 
into  a  sporangium,  which  produces  one  large  compound 
zoospore,  while  special  branches  and  sex-organs  are 
developed  to  produce  the  sex-cells.  The  oogonium 
that  produces  the  egg,  and  the  antheridium  that  pro- 
duces the  sperms,  are  not  only  special  organs  for  produc- 
tion of  these  special  bodies,  but  by  their  structure,  and 
their  position  with  reference  to  each  other,  greatly 
facilitate  the  process  of  fertilization.  The  division  of 
labor  between  nutritive  and  reproductive  organs  is  well 
established.  Furthermore,  the  oospores  are  protected 
by  heavy  walls  as  in  Spirogyra,  which  gives  greater 
chances  of  successfully  surviving  severe  changes  in 
temperature,  moisture,  etc.  It  is  evident  that  Vaucheria 
shows  a  decided  advance  in  complexity. 


5 


COLEOCH^ETE. 

THALLOPHYTES;  ALG-EJ  CHLOROPHYCE.E. 

PRELIMINARY. 

THIS  plant  grows  in  standing  water,  and  is  seen  as 
small  green  disks  on  sticks,  stones,  etc.,  in  quiet  water. 
The  plants  are  quite  small  and  are  not  easily  recognized.1 
When  material  is  found  it  may  be  brought  into  the 
laboratory  on  its  supporting  substance,  and  may  be 
preserved  thus.  Since  the  form  is  rather  rare,  permanent 
mounts  should  be  made  when  good  material  is  found. 

LABORATORY    WORK. 

GROSS   STRUCTURE. 

1.  The  size  and  general  distribution  of  plants  upon  the  sub- 
stratum. 

2.  Color. 

3.  Form.    Are  any  branches  at  margin  of  disk  discernible? 

1  In  many  localities  Coleochate  is  not  abundant,  but  because  of  its 
great  importance  in  the  chain  of  forms  which  illustrate  the  evolution 
of  plants  it  is  introduced,  and  fresh  or  preserved  specimens  should  be 
obtained.  If  material  cannot  be  had,  the  form  should  be  carefully 
studied  from  text  and  manual. 

51 


52  COLEOCH&TE. 

MINUTE  STRUCTURE. 

I.  VEGETATIVE  CHARACTERS. 

Remove  and  mount  some  of  the  plants,  and  by  use  of  the 
low  power  observe: 

1.  The  form  and  arrangement  of  cells  composing  the  plant. 

2.  The  number  of  cells  in  thickness. 

3.  Whether  the  plant  is  a  compact  disk. 
By  using  the  high  power  examine: 

4.  The  details  of  cell-structure  and  arrangement. 

Outline  an  entire  plant  and  draw  in  detail  a  sector  of  the 
plant  from  the  center  of  the  disk  to  the  margin. 

II.  REPRODUCTIVE  CHARACTERS. 

5.  Observe  cases  where  the  disks  may  be  dividing  to  form 
new  ones  vegetatively. 

At  the  tips  of  branches  at  the  edge  of  the  disk  the  sex-organs 
arise.  Note  the  reproductive  structures  as  follows: 

6.  Oogonium,  a    somewhat    elongated    cell    narrowed    ab- 
ruptly into  a  long  tubular   projection  (trichogyne) ;    ob- 
serve the  egg  within  the  oogonium. 

7.  The   antheridia,   small    cells    formed    on    the  marginal 
ends  of  filaments.     Observe  whether  in  those  seen  any 
sperms  are  being  formed.1 

8.  After  the  egg  is  fertilized  the  base  of  the  oogonium  becomes 
encased,  and  after  a  period  of  rest  the  oospore  rearranges 
its  contents  to  form  a  number  of  zoospores  that  escape 
and  grow  into  new  Coleochate  plants.     Try  to  find  some 
of  these  stages.2 

Make  drawings  illustrating  reproductive  structures  of  Coleo- 
chate. 

1  If  good  prepared  slides  are  available,  they  will  be  found  advantageous 
in  the  study  of  6,  7,  and  8. 

3  For  a  good  statement  and  illustration  of  the  details  of  reproduction 
in  Coleochate  see  "Die  Entwickelung  der  Sexualeorgane  bei  Coleochate 
pulvinata,"  by  E.  Oltmanns.  Flora,  85:  1-17,  1898. 


COLEDCH&TE.  $3 


ANNOTATIONS. 

This  plant  is  one  of  the  most  complex  of  all  Chlo- 
rophyceae.  The  plant  body  is  not  filamentous  as  in 
others,  but  the  cells  divide  in  two  planes  and  remain 
closely  joined,  laterally  as  well  as  endwise,  thus  forming 
a  flattened  plate  of  cells  one  layer  in  thickness.  Although 
each  cell  of  the  plant  usually  contains  chlorophyll,  it 
is  evident  that  the  lower  side  will  tend  to  absorb  most 
materials  from  the  substratum,  while  the  upper  side 
is  best  placed  for  chlorophyll  work;  consequently  we 
have  something  like  a  division  of  labor  between  the  dorsal 
and  ventral  sides,  though  the  plant  is  but  one  layer  of 
cells  in  thickness. 

Of  the  sex-organs  the  oogonium  is  more  complex  than 
any  seen  before  in  that  it  has  a  long  hair-like  extension 
from  the  bulbous  base.  This  oogonium  is  not  unlike 
what  we  should  have  if  the  open  end  of  the  Vaucheria 
oogonium  should  become  narrow  and  long.  The  an- 
theridia  are  small  specialized  cells  formed  on  the  tips 
of  marginal  cells,  which  were  originally  nutritive.  In 
this  respect  the  plant  is  less  advanced  than  Vaucheria  and 
resembles  Spirogyra,  all  of  whose  reproductive  cells  are 
for  a  time  nutritive. 

After  fertilization  the  egg  does  not  grow  at  once  into 
a  new  plant,  but  becomes  encased  by  cells  that  grow  up 
around  it,  and  passes  through  a  resting  period.  After 
the  resting  period  the  protoplasm  of  the  oospore  divides, 
forming  a  number  of  zoospores  (usually  eight),  each  of 
which  can  form  a  new  Coleochcete  plant.  Evidently, 
therefore,  we  have  a  sort  of  alternation,  since  the 


54  COLEOCH&TE. 

oospores  form  zoospores,  and  from  the  zoospores  there 
develop  plants  which  after  a  period  of  growth  can  de- 
velop oospores  again.1 

1  It  will  be  profitable  at  this  stage  to  compare  nutritive  structures  and 
the  methods  of  reproduction  in  Ulothrix,  Spirogyra,  Cladophora,  Vau- 
cheria,  and  Coleochate  with  similar  structures  and  processes  in  the  red 
Algse  (Rhodophyceae)  and  in  the  brown  Algae  (Phaeophyceae).  In  addi- 
tion to  laboratory  work,  the  following  references  suggest  sources  of 
information  in  addition  to  the  text  descriptions,  which  all  should  read: 

(a)  Davis,  B.  M.  Development  of  the  cystocarp  in  Champia  parvula. 
Bot.  Gaz.  21 :  109-117,  1896. 

(6)  Fertilization  in  Batrachospermum.  Ann.  Bot.  10:  49-76, 

1896. 

(c)  Farmer,  J.  B.,  and  Williams,  J.  L.    Contributions  to  our  knowledge 
of  the  Fucaceae.      Phil.  Trans.  Royal  Soc.  London.  Ser.  B.  190: 
623-645,  1898. 

(d)  Chester,  Grace  D.     Notes  concerning  the  development  of  Nema- 
lion  muttifidum.    Bot.  Gaz.  21 :  340-347,  1896. 


COMMON     BLACK    MOLD. 

Mucor  stolonijer  (Rhizopus  nigricans}. 
THALLOPHYTES;  FUNGI  J  PHYCOMYCETES. 

PRELIMINARY. 

THE  molds  are  quite  common,  appearing  on  stale 
bread,  damp  leather,  and  decaying  fruits,  sometimes 
as  grayish  fluffy  masses  and  sometimes  as  blue  or  yellow 
coatings  to  their  substrata.  Mucor  may  usually  be 
grown  quite  readily  upon  a  sweet  potato  or  a  piece  of 
moist  bread  kept  at  favorable  temperature  in  a  closed 
glass  dish  or  under  a  glass  bell. 

Although  it  is  an  easy  matter  to  obtain  molds  which 
reproduce  themselves  by  asexual  spores,  it  is  usually 
quite  difficult  to  induce  them  to  undertake  sexual  pro- 
cesses. It  is  supposed  that  Mucor  plants  have  almost 
discontinued  reproduction  by  means  of  sexual  spores. 
However,  zygospores  may  sometimes  be  obtained  by 
growing  the  material  under  a  glass  cover,  keeping  it 
moist,  and  not  in  direct  sunlight,  and  maintaining  a 
constantly  favorable  temperature  of  22°  to  25°  C.1 

1  In  a  brief  article  on  "  Sexual  Reproduction  in  the  Mucorineae  "  by 
A.  F.  Blakeslee  in  Science,  19:  864,  1904,  and  an  extended  discussion 

55 


56  COMMON  BLACK  MOLD. 


LABORATORY   WORK. 

GROSS   STRUCTURE. 

The  vegetative  body  of  the  plant  consists  of  a  network  of 
branches  (mycelium)  upon  and  within  the  material  which 
furnishes  food,  and  upright  branches  from  the  mycelium.  A 
separate  branch  (hypha)  may  pass  through  the  substratum 
and  then  emerge  upon  its  surface  as  an  aerial  stalk.  Observe: 

1.  The  general  appearance  of  the  entire  mass  of  plants. 

2.  The  different  positions  of  the  threads  with  reference  to 
the  supporting  substance. 

3.  Certain  hyphae  which  arise  from  the  mycelium  and  again 
come  in  contact  with  the  substratum,  branching  at  the 
place  of  contact,  and  thus  extend  the  plant. 

4.  The  aerial  hyphae  (sporangiophores)  upon  which  the  black 
tips  (sporangia)  have  formed. 

MINUTE  STRUCTURE. 

I.  NUTRITIVE  STRUCTURES. 

Carefully  remove  a  small  amount  of  the  material  from  its 
substratum,  mount  and  study,  observing : 

1.  The  network  of  hyphae  composing  the  mycelium. 

2.  The  branching  of  hyphae. 

3.  Absence  of  walls  separating  individual  cells;   therefore  it 
is  a  ccenocyte. 

of  the  same  subject  by  the  same  author  in  the  Proc.  Am.  Acad.  of  Arts 
and  Sciences,  40:  205—319,  1904,  it  is  concluded  that  zygospore  forma- 
tion in  the  Mucorinese  "  is  conditioned  by  the  inherent  nature  of  the 
individual  species  and  only  secondarily  or  not  at  all  by  external  fac- 
tors." It  is  further  concluded  that  there  are  two  races  of  Rhizopus 
nigricans  (Mucor  stolonifer],  as  well  as  of  other  Mucorineae.  One  race 
is  monoscious,  the  other  dioecious.  In  order  to  obtain  zygospores  from 
the  dioecious  race  it  is  necessary  to  have  both  positive  and  negative 
strains  growing  together. 


MUCOR  STOLON  I  PER.  57 

4.  From  the  lower  ends  of  some  hyphae  the  root-like  branches 
(rhizoids)  which  penetrate  the  food  material. 

5.  The  granular  protoplasm,  in  some  places  densely  filling 
the  hyphae. 

6.  Draw. 

II.  REPRODUCTIVE  STRUCTURES.    Observe: 

1.  The  sporangia,  in  which  are   blackish  masses  of  spores. 

2.  Stages  in  the  development  of  sporangia,  showing: 

a.  The  tip  of  an  aerial  hypha  beginning  to  become  swollen.1 

b.  This  swollen  tip  separated  from  the  hypha  by  means  of 
a  transverse  wall. 

c.  Young  sporangia  containing  immature  masses  of  spores, 
grayish  in  color. 

d.  Mature  sporangia  with  ripe  masses  of  spores. 

e.  The  broken  sporangium,  the  swollen  tip  of  the  spo- 
rangiophore  (columella),  now  bulged  up  into  the  spo- 
rangium, and  the  free  spores. 

3  Draw. 

4.  Make  a  rough  estimate  of  the  number  of  spores  in  a 
sporangium,  and  count  the  number  of  sporangia  in  one 
mount. 

With  material  that  is  known  to  show  sex-organs  2  observe: 

5.  Branches  that  have  their  tips  greatly  enlarged  and  grow- 
ing toward  one  another. 

6.  Such  branches  whose  ends  have  become  cut  off  by  trans- 
verse walls,  and  are  in  contact. 

7.  The  process  of  union  (conjugation)  of  these  end  cells. 

1  Care  must  be   taken  not  to  mistake  the  swollen  columella  (see  e) 
which  supported  an  old  sporangium,  for  early  stages  in  the  develop- 
ment of  a  young  sporangium.     A  columella  usually  bears  a  scar  which 
shows  where  the  old  sporangium  wall  was  attached. 

2  Unless  there  is  assurance  that  the  material  will  show  sexual  repro- 
duction, no  time  should  be  consumed  with  this  part  of  the  study.     See 
text-books  for  descriptions. 


5§  COMMON  BLACK  MOLD. 

8.  Completed  zygospores  as  the  result  of  conjugation  of  the 
end  cells. 

9.  Draw. 

ANNOTATIONS. 

Fungi  are  devoid  of  chlorophyll  and  consequently  cannot 
utilize  sunlight  and  inorganic  substances  in  initiating  the 
process  of  food  construction.  All  Fungi  must  obtain  food 
at  least  partially  prepared  for  them.  Mucor  may  obtain 
its  nourishment  from  a  variety  of  dead  organic  bodies. 
Its  spores  are  so  abundant  that  the  plant  usually  appears 
when  favorable  conditions  of  growth  are  provided. 

The  branching  ccenocytic  body  of  Mucor  is  quite  like 
some  of  the  Chlorophyceae  among  the  Algae.  The  sexual 
reproduction  recalls  strongly  the  formation  of  zygospores  in 
Spirogyra  and  its  nearest  relatives  among  the  green  Algae, 
and  this  is  taken  to  indicate  a  possible  close  relationship 
between  these  groups,  it  being  supposed  that  Mucor, 
as  well  as  some  other  Fungi  yet  to  be  considered,  have 
descended  from  like  ancestors  with  such  Algae  as  Spirogyra 
and  Vaucheria.  The  gradual  adaptation  to  a  dependent 
habit  of  living  was  doubtless  accompanied  by  the  gradual 
loss  of  chlorophyll,  so  that  the  plants  now  bear  little 
superficial  similarity  to  Algae,  and  only  a  more  detailed 
study  of  the  structures  that  are  least  likely  to  be  affected 
by  such  habits  reveals  the  relationship. 

The  wide  distribution  of  the  molds  and  the  readiness 
with  which  they  grow  on  decaying  substances  must  be 
recognized  as  of  considerable  economic  significance. 
As  agencies  of  decay,  they  not  only  prove  injurious  to 
some  substances,  but  are  helpful  in  reducing  many  others 
to  a  form  again  usable  by  other  plant  life. 


TOADSTOOL   OR*  MUSHROOM. 

THALLOPHYTES;  FUNGI;  BASIDIOMYCETES. 

PRELIMINARY. 

IN  making  this  study  almost  any  common  species  of 
the  group  will  serve  as  a  type.  The  outline  is  prepared 
with  especial  reference  to  the  ordinary  species  of  the 
genera  Agaricus  and  Coprinus.  The  plants  may  be 
found  readily  in  rich  earth  in  warm,  wet  weather,  or 
immediately  following  a  warm  rain.  Those  forms 
which  grow  from  the  ground  rather  than  those  upon 
trees,  stumps,  etc.,  will  usually  answer  best  for  laboratory 
work,  though  representatives  from  different  substrata 
should  be  examined.  All  stages,  from  those  just  emerg- 
ing from  the  ground  to  those  quite  old,  should  be  obtained 
for  laboratory  study;  also  some  of  the  material  on  which 
the  plants  are  growing. 

LABORATORY   WORK. 
GROSS   STRUCTURE. 

Examine  a  fully  formed  "toadstool";  also  one  in  which  the 
top  is  not  yet  easily  distinguished  from  the  stalk,  and  observe: 

1.  The  stalk  or  stipe. 

2.  The  expanded  top,  the  pileus,  on  the  under  side  of  which 
are: 

59 


60  TOADSTOOL  OR  MUSHROOM. 

3.  The  gills. 

4.  At  the  base  of  the  stalk  are  usually  some  fragments  of 
the  mycelium  from  which  the  "toadstool"  grew. 

5.  Divide  a  "toadstool"  lengthwise,  and  observe  the  inner 
structure. 

6.  Dissect  very  young  and  older  specimens,  and  observe: 

a.  The  gill-chambers,  the  floor  of  which  becomes  thinner 
with  age,  and  forms: 

b.  The  veil,  ruptured  as  the  pileus  expands. 

c.  The  ring,  a  scar-like   remnant  of  the  union  of  veil 
and  stalk. 

7.  Make  drawings  illustrating  the  structures  seen. 

MINUTE  STRUCTURE, 
i.  Dissect  carefully  a  piece  of  the  stalk  and  observe  the 

arrangement  of  hyphae  which  compose  it.     Draw. 
With  dissected  material  from  the  gill  or  preferably  with 
especially  prepared  sections  that  we,re  cut  transverse  to  the 
flat  surface  of  the  gill,1  study  its  structure.     Observe: 

a.  A  loosely  interwoven  mass  of  hyphae  in  its  middle,  and  a 
denser  mass  at  the  surface.  What  position  do  the 
ends  of  hyphae  have? 

b.  The  basidia,  club-like  ends  of  hyphae,  which  arise  from 
the  denser  surface  of  the  gill. 

c.  Paraphyses,  the  sterile  filaments  parallel  to  the  basidia. 

d.  The   spores,    a   definite    number   formed   upon   each 
basidium,  each  spore  arising  from 

e.  A  sterigma,  a  short  horn-like  process. 
/.  Draw. 

1  Care  must  be  taken  to  obtain  proper  material  for  such  sections.  If 
it  is  too  old,  the  spores  will  be  gone  from  the  basidia,  and  if  too  young, 
they  cannot  be  readily  demonstrated. 


TOADSTOOL  OR  MUSHROOM.  6 1 

ANNOTATIONS. 

The  Basidiomycetes,  to  which  the  toadstools,  mush- 
rooms, and  puffballs  belong,  are  probably  the  most  con- 
spicuous representatives  of  the  Fungi.  Some  of  the 
forms  are  saprophytic  and  others  are  parasitic  in  their 
way  of  living.  It  is  customary  in  the  entire  group  to 
have  most  of  the  mycelium  growing  within  the  substance 
which  furnishes  food,  and  to  have  the  organs  for  spore 
formation  developed  aerially.  The  main  body  of  the 
structure  ordinarily  called  the  toadstool  is  made  up  of  a 
mass  of  hyphal  threads.  Some  of  these  threads  pass 
through  the  stalk  and  into  the  gills,  and  terminate  in 
club-like  expansions  which  extend  outward  from  the 
surface  of  the  gill.  From  these  club-like  expansions, 
the  basidia,  there  arise  small  tapering  branches  whose 
tips  gradually  enlarge  until  a  spherical  body  is  formed, 
which  finally  becomes  a  spore.  In  some  species  four 
and  in  others  two  such  spores  are  formed.  To  indicate 
the  peculiar  way  in  which  it  is  formed  this  is  called  a 
basidiospore.  The  spores  are  usually  distributed  by 
the  wind,  though  a  variety  of  agencies  may  be  used. 
They  germinate,  and  if  in  favorable  location  develop 
a  new  mycelium  and  eventually  a  new  toadstool.1 

1  Examine  texts  to  discover  the  prevailing  opinions  regarding  ho- 
mologies  between  the  basidium  and  the  sporangium. 


ALBUGO  PORTULAOEoR  A.  CANDIDA. 

THALLOPHYTES;  FUNGI;  PHYCOMYCETES. 

PRELIMINARY. 

THESE  are  very  common  parasitic  Fungi.  A.  Candida 
forms  white  patches  on  the  surface  of  the  leaves,  stems, 
and  flowers  of  many  cruciferous  plants,  such  as  various 
species  of  Capsella,  Sisymbrium,  Lepidium,  Nasturtium, 
Sinapis,  and  Raphanus.  It  is  especially  abundant 
upon  Capsella,  or  "shepherd's-purse,"  from  early  spring 
until  late  in  the  fall,  whitening  and  distorting  the  stems, 
leaves,  and  flowers.  Yet,  notwithstanding  its  luxuriant 
growth,  the  sexual  condition  with  resting  spores  is  not 
abundant  within  the  tissues  of  this  plant,  but  is  produced 
in  great  luxuriance  inside  the  flowers  and  flowering 
branches  of  radish  (Raphanus},  causing  them  to  become 
enormously  enlarged,  sometimes  becoming  even  two  to 
five  centimeters  (one  or  two  inches)  across. 

A.  PortulaccE,  found  upon  the  leaves  of  purslane  or 
"pusley"  (Portulaca  oleracea),  serves  equally  well  for 
this  study,  sex-organs  being  much  more  readily  found 
in  it  than  in  A.  Candida.  A.  Bliti  is  very  common  on 
the  leaves  of  the  common  pigweed  (Amarantus  retro- 
flexus). 

62 


ALBUGO   PORTULAC^E  OR  A.  CANDIDA.  63 

It  is  possible,  with  patience  and  care,  to  make  out  the 
parts  without  the  use  of  special  stains,  but  these  afford 
so  much  assistance  that  they  should  be  used  if  possible.1 

LABORATORY   WORK. 

GROSS  STRUCTURE. 

The  vegetative  body  of  the  plant  consists  of  delicate  trans- 
parent threads,  ramifying  through  the  tissues  of  the  host  on 
which  it  grows,  and  cannot  be  detected  without  the  aid  of  the 
compound  microscope.  In  a  fresh  or  dried  specimen,  observe: 

1.  The  white  blister-like  pustules  on  the  surface  of  the  host, 
the  sori;  their  form.      Observe  the  distortion  and  enlarge- 
ment of  the  stems  and  leaves  where  the  blisters  (sori)  are. 

2.  The  thin  external  membrane,  at  first  entire,  then  becom- 
ing ruptured  in  the  midde. 

3.  The  white  powdery  spores,  conidios pores,  which  drop  out 
upon  jarring,  if  the  specimen  is  dry. 

MINUTE  STRUCTURE. 
I.  ASEXUAL  REPRODUCTION. 

Mount  a  transverse  section  of  a  fresh  or  preserved  specimen 
of  a  stem  or  leaf  bearing  Albugo,  and  under  low  power  observe: 

1.  A  layer  of  short  vertical  filaments,  conidiophores,  which 
appear  to  rise  from  the  tissues  of  the  host  and  bear  on 
their  free  extremities: 

2.  Chains  of  rounded  spores  (conidia),  now  mostly  detached. 

3.  The  ruptured  membrane  consisting  of  the  surface-cells 
of  the  host,  formerly  covering  the  sorus. 

4.  Draw. 

The  vegetative  portion  of  the  plant,  consisting  of  branching 
filaments  pervading  the  tissues  of  the  host,  if  studied  by 

1  For  directions  for  staining  Fungi  see  Chamberlain's  "Methods  in 
Plant  Histology,"  p.  79. 


64  ALBUGO   PORTULAC&  OR  A.  CANDIDA. 

means  of  sections,  requires  excellent  staining  before  it  can 
be  distinguished.  If  the  material  be  boiled  for  one  minute 
in  a  five  per  cent  solution  of  potassium  hydrate,  the  tissues 
may  be  teased  apart  with  needles  and  the  mycelium  exposed. 
Under  high  power,  with  a  good  dissection  or  a  well-stained  sec- 
tion, observe: 

5.  The  conidia;  exact  shape,  wall,  and  contents. 

6.  The    delicate   neck  or  pedicel  supporting  each  conidio- 
spore  before  becoming  detached. 

7.  Draw  a  conidiophore  with  its  conidiospores. 

Trace  a  conidiophore  into  the  tissues  of  the  host  plant,1 
and  observe: 

8.  The  irregular  thickness  of  the  hyphae. 

9.  Whether  it  branches. 

10.  Whether  partition-walls  are  present. 

11.  The  way  in  which  the  hyphae  apply  themselves  to  the  host 
cells.     The  specialized  organs,  the  haustoria,  by  means 
of  which  the  parasite  obtains  food  from  the  host  cells, 
are  found  more  readily  in  the  tissues  of  growing  tips  and 
flowers. 

12.  Draw,  showing  hyphae  and  host  cells. 

Dust  sonre  conidiospores  from  a  fresh  growing  plant 2  upon 
a  slide  and  mount  with  water;  3  in  about  an  hour  observe: 

13.  The  small  protuberance  formed  on  one  side  of  some  of 
the  conidiospores  which  opens  and  permits  the  escape  of 
the  protoplasm  in  the  form  of  several  motile  bodies,  zo- 
ospores. 

1  This  is  not  always  possible,  since  the  hyphse  pass  in  various  direc- 
tions and  many  are  cut  off  in  making  the  section.     The  circular  cut 
ends  may  easily  be  seen. 

2  The  conidia  will  germinate  if  sown  at  any  time  of  day,  provided 
the  specimens  are  fresh,  but  will  do  so  more  readily  when  sown  in  the 
morning  from  plants  which  have  remained  over  night  under  a  moist 
bell-jar. 

1  Care  must  be  taken  that  the  water  does  not  evaporate,  and  to  guard 
against  this  it  is  best  to  keep  the  slide  in  a  moist  chamber. 


ALBUGO  PORTULAC&  OR  A.  CANDIDA.  65 

a.  The  shape  of  the  zoospores,  and  the  pair  of  bright 
spots  in  each. 

b.  Study  the  movement. 

c.  Notice  the  pair  of  delicate  vibratile  cilia,  by  means  of 
which  the  movements  are  effected.     Stain  with  iodin 
and  the  cilia  can  be  seen  more  easily.    Note  their 
length. 

d.  The  color  imparted  to  the  zoospores  and  their  cilia  by 
the  iodin. 

e.  Draw  some  zoospores,  and  also  one  or  two  conidia 
which  have  not  discharged  zoospores,  and  one  or  two 
empty  ones. 

II.  SEXUAL  REPRODUCTION. 

With  a  dissection  or  a  properly  stained  section  of  a  specimen 
containing  oospores,  observe: 

1.  The  numerous  globular  bodies,  distinct  from  and  lying 
in  the  cells  of  the  host,  the  oogonia. 

2.  Accompanying  them,  and  stained  the  same  color,  smaller 
rounded  or  elongated  bodies,  the  antheridia. 

3.  The  way  in  which  the  oogonia  and  antheridia  arise  from 
the  hyphas. 

4.  In  some  of  the  oogonia,  a  globular  mass  of  granular  proto- 
plasm, not  completely  filling  the  oogonium,  the  oosphere. 

5.  A   slender   tube   passing   from   the   antheridium   to   the 
oosphere,  the  fertilizing  tube:   usually  difficult  to  demon- 
monstrate.1     Draw. 

6.  The  development  of  oospores  from  oospheres  as  shown 
by  the  various  stages  in  which  they  have  been  killed. 

1  It  has  been  shown  that  the  fertilizing  tube  brings  nuclei  into  the 
oogonium  and  that  these  unite  with  a  corresponding  number  of  nuclei 
within  the  oospore.  See  figures  in  articles  by  F.  L.  Stevens  on  "The 
Compound  Oospore  of  Albugo  Bliti,"  Bot.  Gaz.  28:  149  and  225;  also 
"Gametogenesis  and  Fertilization  in  Albugo,"  Bot.  Gaz.  32:  77,  157, 
and  238. 


66  ALBUGO  PORTULACM  OR  A.  CANDIDA. 

7.  In  older  oogonia,  more  opaque  bodies,  the  oospores  formed 
from  the  oospheres.     Observe: 

a.  Their  irregular  ridges  on  the  external  wall  of  mature 
oospores. 

b.  The  contents,  in  younger  spores. 

8.  Draw  some  oogonia  and  the  accompanying  antheridia 
showing  different  stages  of  development  of  the  oospheres 
and  oospores. 

ANNOTATIONS. 

In  Albugo  we  have  a  plant  in  some  respects  simple, 
and  in  some  quite  complex.  The  higher  development 
is  shown  in  its  sexual  elements  being  quite  dissimilar 
in  size  and  behavior.  The  larger  female  organ,  the 
oogonium,  receives  the  protoplasm  of  the  smaller  male 
organ,  the  antheridium,  the  former  remaining  in  a  pas- 
sive state,  while  the  antheridium  is  the  active  agent  in 
securing  the  union.  This  is  the  essential  plan  for  all 
higher  plants,  as  well  as  for  some  Algae,  as  has  been 
seen  in  previous  work.  The  transfer  of  the  protoplasm  by 
means  of  a  fertilizing  tube,  and  the  subsequent  forma- 
tion of  a  thick-walled  resting  spore,  bears  a  striking 
resemblance  to  what  takes  place  in  Spirogyra  and 
Vaucheria.  In  both  cases  the  spore  clothes  itself  with 
a  wall  which  differentiates  into  a  delicate  inner  layer  and 
an  outer,  thick,  protective  one.  In  Albugo  this  outer 
wall  is  marked  in  a  manner  characteristic  of  the  species. 
The  oospores  thus  formed  remain  over  winter,  until  the 
tissues  in  which  they  lie  become  disintegrated,  when  they 
are  distributed  by  rain  and  wind,  and  finally  germinate. 

Next  to  the  mode  of  sexual  reproduction  the  most 


ALBUGO   PORTULAC&  OR  A.   CANDIDA.  67 

interesting  feature  of  the  plant  is  its  habit  of  life  and 
the  adaptations  which  have  been  induced  thereby.  It 
is  throughout  its  existence  a  complete  parasite,  growing 
and  feeding  upon  plants  of  very  high  organization.  Being 
no  longer  required  to  elaborate  food  for  itself,  finding  it 
always  at  hand  and  of  superior  quality,  it  possesses  no 
chlorophyll  bodies  by  which  it  might  construct  its  own 
food,  and  is  therefore  quite  colorless.  As  it  grows  it  sends 
its  branches  throughout  all  the  softer  tissues  of  the  host. 
They  do  not  penetrate  the  cells  directly,  however,  but 
push  about  between  them,  and  in  order  to  extract  the 
food  readily,  especially  in  the  newest  portions  where  rapid 
growth  is  taking  place  and  food  is  therefore  abundant, 
send  out  slender  haustoria  which  penetrate  the  adjacent 
cells  and  expand  into  minute  absorbing  bulbs. 

The  means  of  distribution  which  the  plant  possesses 
in  its  oospores  is  rather  limited,  being  inferior  to  that 
of  Spirogyra  and  Vaucheria;  and  when  once  established 
in  a  host  it  is  debarred  from  all  further  locomotion,  such 
as  the  moving  water  imparts  to  the  spores  of  some  other 
plants.  In  order  to  secure  certain  and  extensive  distri- 
bution, therefore,  and  to  provide  for  a  succession  of 
crops  through  the  growing  season,  it  produces  conidio- 
spores  or  summer  spores  in  the  greatest  profusion,  which 
being  light  and  dry  are  easily  blown  about  by  the  wind, 
and  are  ready  to  germinate  at  once.  The  thin  wall  and 
active  protoplasm  of  the  conidia,  from  which  they  derive 
this  advantage,  render  them  at  the  same  time  short-lived, 
so  that  if  a  conidiospore  does  not  find  favorable  con- 
ditions for  growth  within  a  few  hours  after  reaching 
maturity  it  perishes.  The  conidia  germinate  in  water, 


68  ALBUGO   PORTULAC&  OR  A.   CANDIDA. 

and  with  best  results  in  a  film  of  water,  such  as  is  formed 
by  heavy  dew.  To  promote  distribution  still  further, 
each  conidium  often  breaks  up  into  several  active  zo- 
ospores,  which,  after  moving  about  for  fifteen  minutes 
or  so,  finally  come  to  rest,  put  out  a  mycelial  tube  that 
penetrates  the  host,  and  form  a  new  plant.  The  zo- 
o  spores,  except  in  being  colorless  like  the  parent,  remind 
one  of  those  of  Ulothrix,  serving  the  same  purposes  of 
distribution  and  reproduction. 

The  absence  of  septa,  except  for  the  separation  of 
the  antheridia,  oogonia,  and  conidiospores,  making  the 
vegetative  portion  a  continuous  cavity,  is  a  character 
shared  with  Cladophora,  Vaucheria,  and  Mucor,  as  well 
as  many  other  forms,  both  green  and  non-green. 


THE    LILAC    MILDEW. 

Microsph&ra  alni  or  M.  quercina. 

THALLOPHYTES;  FUNGI;  ASCOMYCETES. 

PRELIMINARY. 

THE  lilac  mildew,  Microsphara  alni,  is  extremely  com- 
mon in  the  United  States,  making  the  upper  surface 
of  the  leaves  look  white  and  moldy  from  midsummer  on. 
M.  quercina  is  quite  common  upon  oak-leaves  and  is 
equally  favorable  for  study.  The  first  stage  at  which 
the  Fungus  is  ready  to  gather  is  when  it  appears  powdery, 
which  is  usually  in  June  or  July,  the  earlier  collections 
being  the  best.  The  next  gathering  should  be  made 
in  the  early  part  of  September,  and  another  just  before 
the  leaves  fall.  As  the  leaves  bearing  the  Fungus  are 
gathered,  lay  them  in  a  book  or  plant-press  to  dry.  If 
it  is  possible  to  examine  the  first  stage  with  fresh  material, 
it  will  prove  more  satisfactory,  but  for  the  remainder 
dried  material  will  answer  quite  as  well.  Specimens 
of  the  first  and  second  collections  preserved  in  alcohol 
or  formalin  will  often  prove  helpful  in  the  work. 
69 


70  THE  LILAC  MILDEW. 

LABORATORY  WORK. 

GROSS  STRUCTURE. 

I.  GENERAL  CHARACTERS.    Observe. 

1.  The"distribution  of  the  Fungus  on  the  surface  of  the  leaf. 

2.  The  color. 

II.  THE  CONIDIOSPORES.    Observe: 

i.  The  pulverulent  appearance  on  the  leaves  first  gathered, 
caused  by  the  abundant  conidiospores. 

III.  THE  FRUIT.    Observe: 

1.  The  black  dots  on  the  leaves  gathered  later  in  the  season, 
the  spore-fruits,  or  ascocarps. 

2.  Associated  with  the  black  dots,  other  yellow  ones,  the 
immature  ascocarps. 

MINUTE  STRUCTURE. 

I.  THE  MYCELIUM. 

Scrape  the  Fungus  from  the  surface  of  a  leaf  gathered  in 
early  summer.  First  moisten  it  with  dilute  potassic  hydrate 
if  the  specimen  is  a  dried  one,  and  under  high  power  observe: 

1.  The  colorless  filaments  of  the  mycelium. 

a.  The  branching. 

b.  The  irregular  diameter. 

c.  The  rarity  of  partition-walls. 

2.  Small  lateral  expansions  of  the  filaments,  haustoria,  some- 
what like  irregularly  indented  disks  with  very  short  thick 
stalks,  generally  difficult  to  find. 

3.  Draw. 

II.  CONIDIOSPORES. 

Prepare  a  slide  as  before  from  a  pulverulent  surface,  and 
observe: 


MICROSPH&RA   ALNI  OR  M.  QUERCINA.  71 

1.  The  abundant  conidiospores,  separated  and  free,  owing  to 
the  manipulation. 

a.  Their  shape  and  color. 

b.  The  cell-wall  and  contents. 

2.  The  branches  bearing  conidiospores  (the  conidiophores) 
which  leave  the  mycelial  filaments  at  right  angles,  and 
are    provided  with   cross-partitions  at  regular  intervals, 
and  may  yet  have  some  fully  formed  spores  attached. 

3.  Draw  some  spores,  a  conidiophore,  and  the  hypha  from 
which  it  arises. 

III.  THE  ASCOCARPS. 

Prepare  a  slide  as  before,  but  from  mature  material,  and 
examine  the  ascocarps,  observing: 

1.  The  shape  and  color. 

2.  The  reticulations  of  the  surface. 

3.  The  appendages  extending  out  from  the  sides.     Observe: 

a.  The  number. 

b.  The  color. 

c.  The  length  compared  with  the  diameter  of  the  asco- 
carps. 

d.  The  cross-partitions,  if  any. 

e.  The  manner  of  branching,  and  the  number  of  divisions 
in  each. 

4.  Draw  an  ascocarp  with  its  appendages.     By  pressing  on 
the  cover-glass  with  a  scalpel-handle  or  dissecting-needle, 
crush  the  ascocarps  while  watching  them  through  the 
microscope,  and  observe: 

5.  The  escape  of  sacs  (asci)  containing  spores.     Observe: 

a.  The  number  from  each  ascocarp. 

b.  The  general  shape. 

c.  The  short  pedicel  or  beak  by  which  they  were  attached. 

d.  The  thin  part  of  the  wall  at  the  apex,  not  to  be  seen 
in  every  case. 


72  THE  LILAC  MILDEW. 

e.  The  number  of  spores  (ascos pores)  in  each;  their  shape; 

their  arrangement. 
/.  Draw  an  ascus  with  its  spores. 

6.  Examine  younger  and  younger  ascocarps  to  as  early  a  stage 
as  can  be  found.     Draw. 

IV.  THE  SEX -ORGANS. 

The  very  simple  sex-organs  are  not  easily  found ;  *  if  seen, 
observe: 

1.  The  larger  axial  cell,  the  carpogonium,  homologous  with 
oogonium. 

2.  The  smaller  lateral  cell,  applied  closely  to  the  carpogo- 
nium,  the  antheridium. 

3.  Draw. 

ANNOTATIONS. 

The  group  of  plants  to  which  Microsphara  belongs, 
a  very  large  one,  is  characterized  by  having  a  special 
covering  for  the  spores,  known  as  the  ascus.  This  is 
developed  probably  as  a  result  of  fertilization.  Except 
in  some  of  the  higher  forms,  fertilization  takes  place 
much  as  in  many  other  plants,  but  the  subsequent  devel- 
opment is  very  different,  for  an  outgrowth  of  the  plant 
from  the  portion  immediately  below  the  organs  of  fertili- 
zation at  once  arises  which  eventually  envelops  the  form- 
ing spores  and  develops  into  the  body  of  the  ascocarp. 

It  is  quite  possible  that  Microsph&ra  has  reached  an 
advanced  parthenogenetic  stage,  i.e.  the  "fruits"  may 

1  In  most  material  it  will  not  be  possible  to  find  these  organs.  To 
get  a  good  notion  of  them  examine  the  cuts  illustrating  ascomycete  re- 
production in  the  text-books;  also  in  a  special  article  by  R.  A.  Harper, 
o'n  sexual  reproduction  in  Pyronema  confluens,  and  the  morphology 
of  the  ascocarp;  in  Ann.  of  Bot.  14: 1900.  (This  paper  contains  a  good 
bibliography  of  the  entire  subject.) 


MICROSPH&RA  ALNI  OR  M.  QUERCINA.  73 

be  largely  produced  without  the  transfer  of  protoplasm 
from  the  antheridium  to  the  carpogonium,  which  con- 
stitutes fertilization.  On  this  account  some  other  plants 
better  illustrate  the  fertilization  and  the  early  growth  of 
the  "fruits"  than  the  one  used.  Coleochate,  already 
studied  in  connection  with  Chlorophyceae,  and  Nemalion 
and  Batrachospermum  among  the  red  Algae  illustrate 
the  same  general  process. 

The  comparison  of  Micros ph&ra  with  Albugo  is  very 
instructive  in  showing  how  the  same  conditions  have 
been  reached  by  widely  different  plants.  Both  are 
parasitic,  the  one  living  within  the  host,  and  the  other 
upon  its  surface,  both  deriving  nourishment  by  means 
of  haustoria,  in  addition  to  what  is  absorbed  directly 
through  the  walls  of  the  filaments.1  Both  bear  aerial 
spores,  which  are  formed  by  successive  abstrictions 
from  vertical  mycelial  threads,  the  main  difference  being 
that  in  Albugo  these  must  break  through  the  surface- 
tissue  of  the  host,  and  are  therefore  required  to  grow 
in  groups  in  order  to  exert  the  necessary  force,  while 
in  the  superficial  Microsphara  they  are  single  and  evenly 
distributed.  The  conidiospores  of  Albugo  sometimes 
germinate  by  formation  of  zoospores  and  sometimes 
by  direct  formation  of  a  filament,  while  those  of  Micro- 
sph&ra  grow  into  a  mycelial  filament  at  once,  a  differ- 
ence whose  cause  is  not  known.  Both  plants  form  rest- 
ing spores,  but  in  Albugo  the  protective  covering  is  the 
thickened  wall  of  the  spore;  in  Micros phara  it  is  a 


1  To  see  how  some  of  the  parasites  that  are  closely  related  to  M icro- 
sphara  obtain  their  food  consult  the  drawings  and  text  of  an  article  by 
Grant  Smith  on  "  The  Haustoria  of  Erysipheas."  Bot.  Gaz.  29:  153-184. 


74  THE  LILAC  MILDEW. 

special  shell,  enclosing  a  number  of  pores  in  sacs  in  which 
the  spores  are  formed. 

There  is  not  much  known  of  the  manner  in  which 
these  fruits  pass  the  winter  and  give  rise  in  the  spring  to 
another  growth  of  mildew.  It  is  plain  from  the  structure, 
however,  that  the  spores  escape  from  the  sacs  through  the 
thin  spot  at  their  apex,  but  not  so  evident  how  they 
escape  from  the  shell  of  the  fruit  and  reach  the  host  plant, 
though  their  escape  is  probably  secured  through  the 
gradual  decay  of  the  shell.  The  appendages  we  may 
suppose  are  of  some  service  in  distributing  the  fruits. 


A    LICHEN. 

Physcia  sp.  or  Parmelia  sp. 

THALLOPHYTES. 

PRELIMINARY. 

THESE  plants  may  be  found  growing  upon  the  trunks 
and  branches  of  trees,  upon  wooden  fences  and  some- 
times upon  the  ground.  Parmelia  is  more  common  upon 
hickory- trees.  Physcia  is  quite  widely  distributed.  The 
body  of  the  latter  adheres  closely  to  its  support.  Par- 
melia has  a  body  that  is  thicker,  more  extended,  and 
without  the  prominent  radiating  lines  seen  in  Physcia. 
The  fruiting-cups  in  Physcia  are  small,  with  distinct  and 
regular  cup  margins,  those  in  Parmelia  being  much 
larger  and  more  irregular.  Other  Lichens  are  common 
to  the  locations  given  above. 

Species  of  Cladonia,  as  well  as  numerous  other  genera 
of  Lichens,  will  serve  quite  well  for  this  study,  and  should 
there  be  time  enough,  a  general  study  of  various  forms 
should  be  made. 

75 


76  A   LICHEN. 


LABORATORY  WORK. 

GROSS  STRUCTURE. 

With  a  piece  of  the  support  on  which  is  a  piece  of  the  Lichen 
observe: 

1.  The  color  of  the  Lichen,  both  of  its  upper  surface  and  of 
any  parts  of  the  under  surface  that  can  be  seen.     Com- 
pare the  color  of  wet  and  dry  specimens. 

2.  Its  form. 

3.  How  it  is  attached  to  its  support. 

4.  The  fruiting  cups  (apoihecia)  of  various  sizes. 

5.  Make  a  sketch  showing  the  general  form  of  the  Lichen,  its 
relation  to  its  support,  and  the  apothecia. 

MINUTE  STRUCTURE. 
I.  VEGETATIVE  CHARACTERS. 

Select  a  piece  of  the  body  that  has  been  moistened,  care- 
fully dissect  and  mount  it,  and  observe: 

1.  The   two  elements,  the  Algae  and  Fungi,  that  together 
compose  the  Lichen  body. 

2.  The  form  and  structure  of  each  of  these  elements,  and 
their  similarity  to  any  of  the  plants  previously  studied. 

3.  Cases  where  the  threads  of  Fungi  are  closely  wrapped 
about  the  algal  cells. 

4.  Whether  there  is  any  evidence  that  the  Algae  are  suffering 
from  their  close  contact  with  the  Fungi. 

5.  Make  drawings  showing  the  two  elements  and  their  rela- 
tion to  one  another. 

By  means  of  a  carefully  prepared  cross-section  of  the  Lichen 
body  observe: 

6.  The  layer  formed  of  Fungus  alone,  composing  the  outer 
regions. 


PHY  SCI  A   SP.  OR  FARM  ELI  A   SP.  77 

7.  The  distribution  and  relative  amount  of  Fungus  and  Alga 
in  the  interior  of  the  body. 

8.  The   descending   processes   composed   mainly   of   fungal 
threads  that  connect  the  main  body  of  the  Lichen  with  the 
support. 

9.  Compare  sections  made  from  different  parts  of  the  plant 
body. 

10.  Make  diagrams  showing  the  distribution  of  the  two  ele- 
ments that  compose  the  Lichen. 

11.  REPRODUCTION. 

1.  The  Alga. 

In  the  sections  and  dissections  already  made,  observe: 

a.  Cases  where  the  algal  cells  are  dividing  to  form  new 
ones. 

b.  Whether  abundant  reproduction  is  occurring. 

c.  Compare  the  reproduction  of  this   Alga  with  that  of 
Pleurococcus. 

d.  Illustrate  reproduction  of  the  Alga  by  drawings. 

2.  The  Fungus. 

By  means  of  dissections  or  sections  cut  through  the  apothe- 
cium  and  perpendicular  to  its  upper  surf  ace,  observe: 

a.  The  general  outline  of  the  cup  as  seen  in  section. 

b.  The  general  distribution  of  Algae  and  Fungi  within  it. 

c.  The  surface  of   the  cup  formed   of  parallel  fungal 
threads,  some  club-shaped  sacs — the  asci,  in  which  are 
the  ascospores;   som,e  slender  sterile  threads  crowded 
closely  about  the  asci,  the  paraphyses. 

d.  The  way  in  which  the  ascending  threads  are  associated 
with  the  Algae  that  supply  food  for  the  work  of  repro- 
ducing the  Fungus. 

e.  Draw. 


78  A   LICHEN. 


ANNOTATIONS. 

The  group  of  plants  known  as  Lichens  illustrates  a 
close  symbiotic  relationship  between  chlorophyll-bearing 
and  non-chlorophyll-bearing  plants.  The  combination 
known  as  one  Lichen  is  really  two  plants  living  to- 
gether. The  fact  that  each  is  a  distinct  plant  has  been 
proven  by  growing  the  individuals  out  of  the  Lichen 
combination,  and  by  growing  Lichens  by  bringing  to- 
gether appropriate  Algae  and  Fungi  that  did  not  previ- 
ously live  in  such  an  association. 

The  Fungus  constructs  an  outside  coating  that  seems 
to  protect  the  internal  hyphae  and  the  Algae.  The  Algae 
are  so  placed  as  to  be  well  exposed  to  light,  enabling 
them  to  manufacture  food  used  by  themselves  and  the 
Fungi.  Doubtless  the  Fungi  assist  also  in  the  combina- 
tion by  absorbing  materials,  and  attaching  the  Lichen 
to  its  support. 

Difference  of  opinion  exists  as  to  whether  the  Fungus 
is  a  parasite  upon  the  Algae,  or  whether  both  Alga  and 
Fungi  are  benefited  by  this  habit  of  living.  It  is  known 
that  Lichens  can  live  in  many  positions  and  climates 
where  neither  Fungus  nor  Alga  could  live  alone. 

In  reproduction  each  plant  is  independent,  there  being 
no  Lichen  spore  in  the  sense  that  a  single  such  spore  will 
produce  a  new  Lichen.  It  is  true  that  the  Fungus  uses 
the  Alga  to  nourish  it  in  its  process  of  reproduction,  but 
the  spore  formed  does  not  reproduce  the  Alga. 

The  forms  and  habits  assumed  by  Lichens  are  quite 
varied.  Some  are  almost  invisible  scales  adhering 
closely  to  bark  of  trees  and  walls  of  rocks.  Many  others 


PHY  SCI  A   SP.  OR  FARM  ELI  A   SP.  79 

have  prominent  thallus  bodies  similar  to  those  here 
studied.  Still  others  branch  extensively,  as  the  "reindeer 
moss"  (Cladonia  rangijerina) ,  that  covers  large  areas 
of  ground,  and  the  "bearded  moss"  (Usnea  barbata), 
that  hangs  often  in  long  strings  from  the  branches  of 
trees  in  many  moist  regions. 


A    LIVERWORT. 

Riccia. 

BRYOPHYTES;  HEPATIC^;  RICCIALES. 

PRELIMINARY. 

THIS  plant  is  found  growing  upon  earth,  stones,  etc., 
in  very  damp  places,  one  species,  R.  fluitans,  being  a 
distinctly  aquatic  form.  The  plants  may  be  recognized 
by  their  thick,  dark-green,  dichotomously  branching  small 
bodies,  which  are  sometimes  discoid  with  numerous  rhi- 
zoids  on  the  lower  side.  If  Riccia  cannot  be  obtained, 
the  common  Ricciocarpus  natans  will  answer  for  this 
study,  though  some  structures  are  less  easily  made  out  in 
it  than  in  Riccia.  In  addition  to  the  actively  growing 
plant  bodies,  care  should  be  taken  to  obtain  specimens 
in  which  the  dark  globular  sporophytes  (capsules  im- 
bedded in  the  dorsal  tissues)  can  be  seen.  Material  in 
which  very  young  sporophyte  capsules  can  be  distin- 
guished is  likely  to  contain  a  few  of  the  sexual  organs. 

LABORATORY  WORK. 
GROSS  STRUCTURE. 
With  a  good  specimen  in  hand,  observe: 
i.  The  general  form  of  the  plant. 
80 


RICCIA.  8 1 

2.  Its  method  of  branching. 

3.  Its  basal  and  apical  regions. 

4.  Its  differentiation  into  dorsal  and  ventral  sides. 

5.  The  definitely  organized  midrib. 

6.  The  dark  sporophyte  bodies  sometimes  seen  along  the 
midrib. 

7.  Rhizoids,  on  the  ventral  surface. 

8.  Draw. 

MINUTE  STRUCTURE. 

Make  a  thin  transverse  section  of  the  plant  body  (thallus) 
and  mount  in  water. 

I.  VEGETATIVE  STRUCTURES.    Observe: 

1.  Whether   a   distinct   non-chlorophyll-bearing  layer  (epi- 
dermis) is  developed  above  and  below. 

2.  The  rhizoids;  length,  structure,  and  the  way  in  which  they 
are  attached  to  the  lowest  layer  of  body  cells. 

3.  Structure  and  arrangement  of  chlorophyll-bearing  cells, 
the  lower  cells  rather  compact,  while  toward  the  dorsal 
surface  are  rows  of  green  cells  between  which  are  irreg- 
ular air-spaces. 

4.  Draw. 

II.  SEXUAL  REPRODUCTION. 

Using  the  same  section  observe  that: 

1.  Along  the  midrib  sometimes  there  may  be  seen  the  deeply 
imbedded  flask-like  archegonia  and  the  club-shaped  an- 
theridia.1 

2.  In  the  swollen  part,  the  venter  of  the  archegonium,  is  the 
central  cell,  which  is  the  egg,  above  which  is  one  ventral 

1  The  sex-organs  of  Riccia  are  not  easily  demonstrated.  Numerous 
sections  will  be  required  to  perform  all  the  work  outlined.  Specially 
prepared  sections  will  be  found  helpful  in  the  work.  For  making  sec- 
tions of  liverwort  sex-organs  see  Chamberlain's  "Methods  in  Plant 
Histology,"  p.  89. 


82  A   LIVERWORT. 

canal  cell,  and  a  row  of  neck  canal  cells,  enclosed  by  the 
neck  wall  cells.  In  archegonia  which  contain  fertilized 
eggs  the  canal  cells  have  disappeared,  having  become  dis- 
organized to  permit  the  access  of  the  sperms  to  the  eggs. 

3.  Draw. 
Observe  also: 

4.  The  antheridium,  a  club-shaped  organ,  consisting  of  a 
layer  of  wall  cells  and  many  small  sperm  mother-cells. 
In  fresh  material  sperms  may  sometimes  be  seen  as  they 
escape  from  the  antheridium. 

5.  Draw. 

6.  Archegonia  which  contain  germinating  oospores. 

7.  Draw. 

III.  ASEXUAL  REPRODUCTION. 

1.  If  the  section  is  especially  favorable,  note  the  different 
stages  in  the  germination  of  the  oospores,  resulting  finally 
in  the  formation  of  the  fully  formed  sporophyte  (or  spo- 
rogoniurri),  consisting  of: 

(a)  A  single  outside  layer  of  cells  constituting  the  wall 
which  early  disappears,  and 
(6)  A  mass  of  asexual  spores. 

2.  Draw. 

ANNOTATIONS. 

The  general  form  and  structure  of  Riccia  suggest 
Coleochcete,  the  highest  member  of  the  Chlorophyceae 
that  we  have  examined,  but  Riccia  is  very  much  more 
highly  differentiated  both  for  nutritive  and  reproductive 
work.  The  prostrate  branching  body  of  Riccia  is 
differentiated  in  that  it  is  distinctly  dorsiventral,  has  on 
its  ventral  side  rhizoids  which  perhaps  assist  in  obtaining 
water  and  its  solutes  and  serve  also  to  anchor  it.  The 


RICCIA.  83 

plant  body  has  further  specially  organized  chlorophyll- 
bearing  cells  and  protecting  epidermal  cells.  Altogether 
the  plant  is  very  much  better  organized  for  chlorophyll 
work  than  is  Coleochate. 

The  sexual  organs  of  Riccia  are  multicellular  and 
are  nearly  enclosed  by  vegetative  tissues.  They  are  not 
imbedded  when  they  begin  to  develop,  but  become  so  as 
the  adjacent  tissues  grow  over  them.  The  biciliate 
sperms  are  discharged  on  the  upper  surface  of  the  plant 
and  gain  entrance  to  the  egg  through  the  canal  of  the 
archegonium. 

After  fertilization  the  egg  does  not  pass  through  a 
resting  period,  but  soon  begins  to  germinate  without 
being  set  free  from  the  venter  of  the  archegonium.  It 
develops  a  globular  mass  of  cells,  of  which  the  outermost 
layer  produces  no  spores  (i.e.,  it  is  sterile),  but  encloses 
the  spore-forming  or  sporogenous  tissue  within.  This 
sporogenous  tissue  finally  forms  a  mass  of  heavy  rough- 
walled  spores,  that  are  eventually  set  free  by  the  early 
disappearance  of  the  wall  and  ultimately  by  the  decay 
of  the  old  plant  body.  At  the  return  of  favorable  con- 
ditions for  growth  these  spores  produce  new  Riccia 
plants. 

It  is  evident  that  we  have  two  kinds  of  spores  formed, 
one  as  the  result  of  the  union  of  the  sperm  and  the  egg, 
and  another  as  the  result  of  development  of  this  oospore. 
One  is  sexual,  the  other  asexual.  The  number  of  asexual 
spores  formed  is  quite  large  relatively,  and  serves  very 
greatly  to  increase  the  number  of  new  plants  that  may 
come  from  one  oospore.  The  sporogonium,  the  structure 
formed  from  the  oospore,  is,  when  ripe,  little  more  than 


84  A   LIVERWORT. 

a  mass  of  spores,  but  in  higher  plants  it  will  be  seen 
to  have  developed  into  the  structure  we  ordinarily  regard 
as  the  plant  body.  In  Coleoch&te  the  oospore  becomes 
enclosed  by  a  heavy  wall  of  cells,  and  finally  forms  a 
mass  of  asexual  spores  that  form  new  Coleochcete 
plants.1  Even  in  it  we  have  the  same  sort  of  alternation 
between  sexual  and  asexual  spores  that  we  have  in  Riccia, 
while  we  also  have  similarities  existing  in  the  two  plants 
both  as  to  the  form  of  the  plant  body  and  the 
organs  producing  asexual  spores.  The  structure  that 
grows  from  the  oospore  is  little  more  than  an  organ 
for  producing  asexual  spores,  but  it  is  destined  in  the 
course  of  evolution  to  become  more  and  more  important 
until  it  is  the  dominant  phase  in  the  plant's  life-cycle. 

1  It  must  be  borne  in  mind  that  in  Coleockcete  the  protecting  tissue 
about  the  resting  oospore  did  not  come  from  the  oospore,  as  is  true  in 
Riccia.  See  Davis  on  "The  Origin  of  the  Sporophyte,"  in  the  Ameri- 
can Naturalist,  37:  411. 


MARCHANTIA    POLYMORPHA. 

BRYOPHYTES;          HEPATIC^;      MARCHANTIALES. 

PRELIMINARY. 

THIS  liverwort  is  common  throughout  America  and 
Europe.  It  grows  among  grass,  over  wet  soil  or  rocks, 
in  drier  spots  along  walls  and  fences,  and  occasionally 
in  more  exposed  situations,  but  is  most  luxuriant  in 
damp  shady  places.  The  vegetative  part  consists  of 
a  flat,  green,  leaf-like,  dorsiventral  body,  on  the  under 
side  of  which  are  rhizoids  that  hold  it  close  to  the  ground. 
Often  the  plants  may  be  distinguished  by  the  presence 
of  reproductive  branches  that  arise  as  stalks  from  the 
flat  part  of  the  main  body,  and  bear  expanded  heads 
at  their  upper  ends.  Besides  these  there  are  often  small 
sessile  cups,  the  cupules,  on  the  upper  surface  of  the 
stems.  On  the  dorsal  surface  the  plant  is  divided  into 
very  small  diamond-shaped  areas.  When  the  repro- 
ductive branches  and  cupules  are  present  Marchantia 
may  easily  be  recognized.  Conocephalus  conicus,  another 
liverwort  that  grows  in  damp  places  and  bears  a  strong 
general  resemblance  to  Marchantia,  may  be  distinguished 
by  its  much  more  prominent  diamond-shaped  areas,  and 
the  more  prominent  pore  that  is  visible  to  the  naked  eye 
85 


86  MARCHANTIA   POLYMORPHA. 

within  each  area.  Lunularia  cruciata  is  not  uncommon 
in  greenhouses.  It  may  be  distinguished  by  its  crescent- 
shaped  cupules,  lacking  a  border  on  one  side. 

Marchantia  may  be  grown  in  the  laboratory.  In 
collecting  material  for  study,  care  should  be  taken  to 
obtain  fertile  plants  with  young  heads;  some  female 
heads  just  large  enough  to  be  seen  in  the  sinus  at  the 
tip  of  the  branch  should  be  collected.  Also  a  good 
supply  of  older  heads  of  both  flat  and  radiate  forms  will 
be  needed. 

LABORATORY  WORK. 

GROSS  STRUCTURE. 

I.  VEGETATIVE  STRUCTURE.     By  examining  one  or  two  speci- 

mens, observe: 

1.  The  general  form  and  color  of  the  body. 

2.  Its  manner  of  branching. 

3.  The  rhizoids. 

4.  The  diamond-shaped  areas,  with  a  central  air-pore  in  each. 
These  are  seen  best  with  a  small  lens. 

5.  Draw. 

II.  REPRODUCTIVE  STRUCTURES.     Observe: 

1.  In  rather  large  patches  of  Marchantia  note  how  the  younger 
parts  of  the  plants  have  advanced,  and  have  been  left  free 
as  new  plants  by  the  death  of  the  older  portion. 

2.  Two  kinds  of  heads  on  the  upright  branches.     The  flat 
disk-like  one  is  the  anther -idiot  head,  and  the  radiate  or 
fingered  one  is  the  archegonial  head.     Determine  whether 
both  kinds  are  borne  on  the  same  plant. 

3.  The  cupules,  their  form,  and  where  borne;  the  small  green 
buds,  the  gemma,  within  the  cupules. 

4.  Make  general  sketches  illustrating  reproductive  structures. 


MARCHANTIA   POLYMORPHA.  87 

MINUTE  STRUCTURE. 

I.  VEGETATIVE  STRUCTURE. 

Remove  the  outgrowths  from  the  under  surface  on  different 
parts  of  the  plant,  mount,  and  observe: 

1.  Flat  outgrowths;  note  where  and  how  attached.1 

2.  Two  kinds  of  tubular  rhizoids,  one  with  peculiar  thick- 
enings within  them. 

3.  Draw. 

Make  a  thin  cross-section  of  the  plant  body,  and  observe: 

4.  Lower  epidermis  from  which  the  rhizoids,  etc.,  arise. 

5.  A  compact  mass  of  almost  or  entirely  achlorous  (without 
chlorophyll)  tissue  directly  above  this  epidermis. 

6.  Special  chlorophyllose  cells,  often  in  alga-like  chains  that 
extend  from  the  compact  tissue  toward  the  upper  surface. 

7.  The  upper  epidermis,  in  which  sections  of  the  pores  will 
sometimes  be  seen. 

8.  Just  beneath  the  upper  epidermis,  and  extending  down  to 
the  compact  sterile  tissue,  the  columns  of  pale  cells,  which 
are  sections  of  the  partitions  which  divide  the  upper  part 
of  the  plant  into  diamond-shaped  air-chambers,  in  which 
are  the  chains  of  chlorophyllose  cells. 

9.  Draw. 

II.  VEGETATIVE  REPRODUCTION. 

i.  The  cupules  and  gemmse.    Remove  and  study  the  form 
of  gemmae.     Observe: 

a.  The  flattened  body. 

b.  The  pair  of  notches  indicating  the  points  of  most  active 
growth. 

c.  The  scar  at  the  point  where  the  gemma  separated  from 
the  stalk  upon  which  it  grew. 

1  These    plate-like  outgrowths    are  regarded   as  primitive  leaf-like 
structures. 


88  MARCHANTIA    POLYMORPHA. 

d.  Make  a  vertical  section  through  the  base  of  the  cup, 
and  observe  stages  in  the  development  of  gemmae. 

e.  Draw. 

III.  SEXUAL  REPRODUCTION. 

1.  The  antheridial  branch,  and  antheridia. 

Select  an  antheridial  branch  in  which  the  stalk  is  rather 
large  and  make  a  cross-section  of  it.     Observe: 
a.  The  general  outline  of  the  section. 
6.  The  hairs  which  fill  the  grooves.     Follow  some  of  the 
strands  of  the  hairs  downward  and  upward  upon  an 
uninjured  stalk  and  determine  where  they  terminate. 

c.  Sketch  the  section. 

Make  radial  vertical  sections  of  the  head,  and  observe: 

d.  The  prominent  flask-like  chambers,  with  their  necks 
opening  upon  the  upper  surface,  each  containing  an 
antheridium  within  it. 

e.  The  antheridium;   its  stalk;  wall  of  one  layer  of  cells, 
within  which  are  many  squarish  cells,  the  sperm  mother- 
cells.1 

/.  The  air-cavities  and  tissues  which  compose  the  body 

of  the  head. 

g.  Young  and  old  stages  of  antheridia. 
h.  Draw  enough  of  the  section  to  show  these  structures. 

2.  The  archegonial  branch,  and  archegonia. 
Select  both  old  and  young  branches,  and  observe: 

a.  The  appearance  of  young  branches  at  the  time  they 

first  may  be  distinguished  from  the  thallus. 
Then  carefully  dissect  the  young  head  and  mount,  or  by 
means  of  a  radial  vertical  section  observe: 

1  With  fresh  material  often  an  abundance  of  swimming  sperms  may 
be  obtained.  This  may  be  done  by  placing  a  fresh  ripe  head  in  a 
drop  of  water,  at  which  time  thousands  of  sperms  may  escape  from  their 
antheridia.  They  may  be  studied  first  while  moving,  and  then  staining 
with  iodin  will  give  an  excellent  view  of  their  structure. 


MARCHANTIA    POLYMORPHA.  89 

b.  The  archegonia,  which  in  such  material  usually  appear 
in  various  stages  of  development.     With  a  fully  formed 
archegonium  locate  the  following  parts: 

i.  The  elongated  basal  region,  the  stalk. 
ii.  The  swollen  region,  the  venter. 
iii.  The  elongated  region,  the  neck. 
iv.  Within  the  venter,  the  egg.     Frequently  it  will  be 
seen  that  the  egg  has  been  fertilized  and  has  already 
begun  to  germinate, 
v.  Within  the  neck,  the  neck  canal  cells. 
vi.  The  cell  between  the  neck  canal  cells  and  the  egg, 
the  ventral  canal  cell. 

c.  Arising  from  the  region  near  the  base  of  the  archegonium, 
an  outgrowth,  the  perianth,  which  later  develops  about 
the  archegonium. 

d.  Draw  a  fully  formed  archegonium. 

e.  Draw  stages  in  the  development  of  an  archegonium. 

/.  Note  the  changes  in  the  size  and  form  of  the  archegonial 
heads  as  they  mature. 

IV.  THE  SPOROPHYTE  AND  ASEXUAL  REPRODUCTION. 

Make  sections  of  an  archegonial  head  that  is  more  mature 
and  study  the  changes  that  occur  in  the  germination  and 
development  of  the  oospore.  Observe: 

1.  The  first  division  of  the  oospore  by  the  basal  wall. 

2.  Trace  the  changes  in  form  of  the  body  and  the  increase 

in  the  number  of  cells  until  the  number  can  no  longer  be 
determined. 

3.  Draw. 

From  old  heads  dissect  out  the  fully  formed  sporophytes 
enveloped  by  the  perianth,  and  observe: 

4.  The    three    distinct    regions,    joot,    stalk,   and    capsule. 
Draw. 

5.  The  spores. 


90  MARCHANTIA   POLYMORPHA. 

6.  The  elaters,  elongated  cells,  with  spiral  thickenings.    Re- 
move the  cover-slip  and  allow  the  crushed  specimen  to 
become  dry  as  you  watch  it,  and  observe: 

7.  The  behavior  of  the  elaters. 

8.  Draw. 

ANNOTATIONS. 

From  a  morphological  point  of  view  Marchantia  is  a  plant 
of  unusual  interest,  on  account  of  its  remarkable  degree 
of  differentiation.  The  upper  part  of  the  prostrate  game- 
tophyte  has  differentiated  highly  specialized  tissues  for 
chlorophyll  work,  the  whole  upper  surface  being  divided 
into  air-chambers  in  which  we  find  chlorophyllose  cells, 
that  show  a  striking  resemblance  to  the  green  Algae.  This 
air-chamber  is  open  to  the  exterior  by  a  pore  whose 
edge  is  formed  by  four  layers  of  cells.  The  lower  part 
of  the  body  is  differentiated  for  the  work  of  support 
and  storage  of  foods,  and  must  also  transfer  materials 
from  the  ventral  surface  up  to  the  chlorophyll  tissue. 

As  the  gametophytes  grow  they  branch  dichotomously, 
the  older  parts  steadily  dying  away,  thus  giving  rise  to 
separate  plants.  Vegetative  reproduction  is  also  carried 
on  freely  by  means  of  gemmae,  designed  especially  for 
the  purpose,  and  borne  in  special  organs.  The  plant  is 
extremely  successful  in  its  vegetative  reproduction. 

The  sexual  reproduction  also  shows  an  advance  over 
Riccia.  Special  branches  bear  the  sexual  organs,  the 
sexual  organs  themselves  being  more  complex  than 
in  Riccia;  furthermore,  one  plant  bears  but  one  kind  of 
sex  organ,  i.e.,  the  species  is  dioecious. 

Fertilization  takes  place  within  the  venter  of  the 
archegonium,  and  the  oospore  germinates  in  the  same 


MARCHANTIA    POLYMORPHA.  9 1 

location.  The  oospore  is  first  divided  by  the  basal 
wall  into  two  regions,  one  of  which  develops  the  foot 
of  the  sporophyte,  and  the  other  develops  the  capsule. 
The  wall  layer  of  this  capsule  is  sterile,  and  within  this 
the  spores  are  produced.  Distributed  about  among  the 
spores  are  elaters,  specialized  structures  that  move  the 
spores  about  and  usually  hold  several  of  them  together. 
It  will  be  noted  also  that  the  sporophyte  of  this  plant  has 
relatively  more  sterile  tissues  than  has  the  sporophyte  of 
Riccia,  there  being  in  addition  to  the  sterile  walls  and 
elaters,  the  foot  and  stalk,  which  place  the  spores  in 
a  position  more  favorable  for  distribution. 


A    LEAFY     LIVERWORT. 

Porella. 

BRYOPHYTES;  HEPATIC^;          JUNGERMANNIALES. 

PRELIMINARY. 

Porella  is  common  in  temperate  regions,  appearing 
as  a  moss-like  growth  upon  logs,  tree-trunks,  etc.  It 
lies  almost  prostrate,  with  the  tips  of  branches  somewhat 
turned  up.  It  can  undergo  extreme  drying  and  retain 
its  vitality.  Material  collected  for  study  may  be  pre- 
served by  drying  or  in  the  ordinary  preserving  fluids. 
For  the  study  there  should  be  specimens  showing  the 
vegetative  structures,  and  also  some  showing  reproduc- 
tive organs.  The  latter  may  usually  be  detected  by  the 
tufted  arrangement  of  the  leaves  at  the  tips  of  branches 
on  which  there  are  reproductive  organs.  The  archegonia 
and  antheridia  are  not  borne  on  the  same  branches. 

LABORATORY  WORK. 
GROSS  STRUCTURE. 

With  a  few  specimens  in  hand  and  by  use  of  a  hand-lens 
observe: 

i.  The  central  axis  or  stem  of  the  plant  from  which  arise: 
92 


PORELLA.  93 

2.  The  leaves;   note  the  way  in  which  they  are  attached  to 
the  stem,  the  number  of  rows,  their  positions,  and  their 
arrangement  at  the  tips  of  branches. 

3.  Rhizoids;   their  number  and  position. 

4.  Draw. 

MINUTE  STRUCTURE. 

I.  VEGETATIVE  STRUCTURE. 

Mount  two  or  three  of  the  leaves  and  observe: 

1.  General   structure,    thickness,    arrangement   of   plastids, 
presence  or  absence  of  epidermis  and  midrib. 

2.  The  way  in  which  the  leaves  join  the  stem. 
Mount  some  of  the  rhizoids,  and  observe: 

3.  Their  general  structure;    compare  with  the  rhizoids  of 
Marchantia. 

4.  Draw. 

II.  REPRODUCTIVE  STRUCTURE. 

1.  Select   branches  on   the  tips   of  which  the  leaves  have 
formed  close  tufts,  carefully  dissect  away  the  leaves  and 
search    for   archegonia l  in  different  stages  of  develop- 
ment.     Draw,  showing  archegonial  base,  venter,   neck, 
neck  canal  cells,  and  egg. 

2.  On  other  branches,  having  leaves  more  regularly  imbri- 
cate than  the  vegetative  ones,  search  for  the  antheridia, 
each  made  up  of  a  long  stalk  bearing  a  spherical  body  in 
which  sperms  are  formed.     It  is  frequently  possible  also 
to  observe  good  stages  in  the  development  of  the  anthe- 
ridia.    Draw. 

3.  On   old   archegonial  branches  find  the  sporophytes,  each 
bearing  a  general  resemblance  to  an  antheridium.    Search 

1  Specially  sectioned  and  stained  preparations  cut  parallel  to  the 
stem  of  the  branches  will  be  found  advantageous  in  studying  archegonia, 
antheridia,  and  sporophytes. 


94  A   LEAFY  LIVERWORT. 

for  oospores  just  beginning  to  develop  the  sporophyte, 
and  also  old  sporophytes  which  contain  ripe  spores. 
Draw. 

ANNOTATIONS. 

The  plant  body  of  the  leafy  liverworts  .  differs  from 
that  of  the  forms  already  studied  in  that  it  has  specialized 
stem  and  leaves,  better  adapting  it  for  chlorophyll 
work.  The  leaves  are  arranged  in  three  rows  and 
are  simply  lateral  outgrowths  from  the  stem.  The 
rhizoids  are  comparatively  few  in  number  and  arise 
from  the  ventral  side  of  the  stem  at  its  base.  Al- 
though the  plant  has  basal  and  apical  regions  and  the 
leaves  are  arranged  around  the  stem,  it  is  essentially 
dorsiventral  because  of  the  unlikeness  of  the  leaves 
above  and  below,  and  of  the  occurrence  of  rhizoids 
chiefly  on  the  ventral  side.  The  plant  is  prostrate, 
though  the  tip  sometimes  becomes  erect.  In  some 
ways  the  plant  is  far  better  organized  for  nutritive  work 
than  any  that  have  yet  been  considered. 

In  Porella  the  branches  that  bear  the  reproductive 
organs  are  not  set  apart  entirely  for  reproductive  work,  as 
was  the  case  in  Marchantia.  In  general  structure  the 
archegonium  is  essentially  similar  to  that  of  Marchantia, 
while  the  antheridium  is  not  sunk  beneath  the  surface  as  in 
the  other  liverworts  studied,  but  is  free  and  has  a  support- 
ing stalk.  Fertilization  takes  place  and  the  oospore  devel- 
ops into  the  sporophyte  as  in  Marchantia.  The  sporo- 
phyte has  distinct  foot,  stalk,  and  capsule  regions.  When 
it  has  ripened  its  globular  mass  of  spores  they  are  set 
free  by  having  the  capsule  split  into  four  valves,  and 
eventually  develop  new  leafy  plants. 


ANTHOCEROS. 

BRYOPHYTES;          HEPATIC^;      ANTHOCEROTALES. 

PRELIMINARY. 

THIS  liverwort  is  not  so  common  as  are  the  two  already 
studied,  but  may  be  found  frequently  on  wet  ground 
or  stones  in  deeply  shaded  places  or  even  in  dense  growth 
of  grass.  Its  thallus  is  usually  smaller  than  that  of 
Riccia,  and  often  appears  as  a  small  scale-like  green 
body,  adhering  very  closely  to  its  support.  The  plant 
is  easily  identified  when  sporophytes  are  present,  since 
they  are  prominent  dark  green  slender  columns  which 
stand  upright  from  the  flat  thallus.  Material  for  study 
should  consist  of  the  thallus,  both  in  vegetative  and 
reproductive  periods,  and  of  those  bearing  sporophytes.1 

LABORATORY  WORK. 
GROSS  STRUCTURE. 

With  some  specimens  in  a  small  dish  of  water  observe: 

1.  The  size  of  the  thallus  as  compared  with  Riccia  and  Mar- 
chantia. 

2.  The  form. 

3.  Thickness,  at  the  margins  and  along  the  midrib. 

1  Owing  to  the  peculiar  importance  of  Anthoceros  in  illustrating  the 
development  of  the  plant  kingdom,  suitable  material  should  be  obtained 
from  a  supply  house  in  case  the  local  region  does  not  furnish  it. 

95 


96  ANTHOCEROS. 

4.  Rhizoids:    number  and  distribution. 

5.  Draw. 

6.  Sporophytes  arising  from  the  thallus.     Note  especially  the 
form  and  relative  size  of  all  parts  of  the  sporophyte,  and 
whether  its  tip  is  split  or  entire. 

7.  Draw. 

MINUTE  STRUCTURE. 

I.  VEGETATIVE  STRUCTURES. 

By  use  of  sections  of  the  thallus  cut  at  right  angles  to  the 
surface  and  parallel  to  the  midrib  observe: 

1.  The  relatively  simple  structure  of  the  thallus. 

a.  Number  of  cells  in  thickness  at  midrib  and  margin. 

b.  Absence  of  epidermal  tissue. 

2.  Origin  of  rhizoids. 

3.  Draw. 

II.  SEXUAL  REPRODUCTION.1 

1.  Archegonia  and  antheridia,  somewhat  similar  to  those  of 
Riccia,  though    the    antheridia    arise    from    within    the 
gametophyte  tissue  (endogenous). 

2.  The  oospore  beginning  to  germinate  to  form  the  sporo- 
phyte. 

3.  Draw. 

III.  ASEXUAL  REPRODUCTION. 

1.  The  base  of  a  well-developed  sporophyte.     Note  especially 
the  foot,  with  its  rhizoid-like  processes  which  penetrate 
the  tissues  of  the  thallus. 

2.  Draw. 

By  use  of  a  section  cut  lengthwise  through  the  sporophyte 
observe: 

1  Owing  to  the  difficulty  of  observing  these  points,  prepared  slides  spe- 
cially stained  are  indispensable  and  should  be  used  as  a  means  of 
demonstrating  the  structures  mentioned  in  i  and  2. 


ANTHOCEROS.  97 

3.  That  the  structure   is  organized  into  three  regions,   an 
outer    protecting,    supporting,    and    chlorophyll-bearing 
region;    an  axial  region;    and  between  these  the  spore- 
forming  or  sporogenous  region. 

4.  In  the  sporogenous  region,  the  stages  in  the  process  of 
spore  formation,  from  youngest  sporogenous  tissue  in  the 
lower  part  of  the  sporophyte,  to  fully  formed  spores  toward 
the  tip. 

5.  Draw,  showing  different  kinds  of  tissues,  and  stages  in 
spore  formation. 

ANNOTATIONS. 

The  gametophyte  body  of  Anthoceros  is  very  much 
more  simple  than  that  of  Riccia.  It  has  no  special  air- 
chambers  or  air-pores,  is  but  a  few  layers  of  cells  in  thick- 
ness in  the  thickest  place,  and  in  every  way  suggests  a 
very  simple  type  of  plant-body.  The  archegonia  and 
antheridia  are  simple  in  structure.  The  archegonia 
develop  from  surface  cells  and  become  surrounded  by 
gametophyte  tissue  while  antheridia  are  endogenous  in 
origin.  The  fertilized  egg  begins  its  development  while 
imbedded  in  the  archegonium.  From  this  oospore  there 
develops  a  sporophyte  which  is  much  more  complex  than 
any  heretofore  considered.  The  sporophyte  is  distinctly 
stalked  and  bears  at  its  lower  end  structures  like  short 
rhizoids  which  serve  to  increase  the  surface  through 
which  the  foot  absorbs  nourishment  from  the  gameto- 
phyte. In  addition  to  this  there  are  stomata,  like  those 
of  higher  plants,  and  chlorophyll  that  enables  the  sporo- 
phyte to  manufacture  some  of  its  own  food.  It  is  evi- 
dent that  the  sporophyte  is  somewhat  independent,  and 
to  become  completely  so  it  needs  but  to  have  the  root- 


98  ANTHOCEROS. 

like  foot  become  adapted  to  the  ground,  and  the  chloro- 
phyllose  tissue  increased.  This  course  of  development 
for  the  foot,  however,  was  never  worked  out,  or  at  least 
has  not  survived.  This  is  the  highest  type  of  sporophyte 
found  in  the  liverworts,  and  gives  a  hint  of  the  inde- 
pendent sporophyte  of  the  Pteridophytes  soon  to  be  con- 
sidered. 

The  asexual  spores  of  Antlwceros  are  formed  in  the 
extended  portion  or  capsule,  the  oldest  being  at  the  top 
and  the  youngest  below  Only  a  cylinder  of  tissue  is 
used  to  produce  spores,  all  the  remaining  part  being 
differentiated  to  serve  other  functions.  It  is  evident 
that  we  have  had  a  relative,  though  probably  not  an 
absolute,  diminution  of  the  amount  of  sporogenous  tissue, 
and  corresponding  increase  of  sterile  tissues  from  the 
lowest  to  the  highest  liverworts.  This  has  been  accom- 
panied by  increase  hi  the  complexity  of  the  sporophyte 
body,  and  constant  approach  toward  independence.1 

1  See  article  by  Bradley  Moore  Davis  on  "The  Origin  of  the  Spore- 
phyte,"  already  cited  in  connection  with  CoUoduzte, 


A   MOSS    PLANT. 

Funaria  hygrometrica  or  Atrichum  undulatum. 

BRYOPHYTES;  MUSCI;  BRYALES. 

PRELIMINARY. 

To  those  who  are  entirely  unfamiliar  with  the  mosses, 
the  different  species  appear  quite  similar.  There  are 
many  species  besides  the  two  mentioned  that  are  suitable 
for  laboratory  study,  but  the  ones  mentioned  are  abundant 
and  are  more  readily  obtained  in  all  their  stages  than  are 
some  of  the  others.  Although  the  outline  has  been 
prepared  with  a  view  to  the  use  of  Funaria  or  Atrichum, 
it  may  be  adapted  readily  to  any  other  common  form. 

Atrichum  is  widely  distributed  and  very  common, 
forming  carpet-like  patches  in  woods  and  on  shady 
banks.  Funaria  has  even  a  wider  distribution  than 
has  Atrichum,  and  has  an  additional  advantage  as  a 
type  for  study  in  that  it  is  more  readily  grown  in  the 
laboratory.  It  is  found  especially  where  fires  have 
burned,  or  on  cinder  paths.  As  the  reproductive  organs 
of  Funaria  are  formed  rather  early  in  the  growing  season, 
it  is  necessary  to  collect  specimens  in  the  latter  part  of 
March  and  during  April,  in  order  to  obtain  plants  showing 
good  antheridia  and  archegonia.  The  antheridial  plants 
99 


100  A   MOSS  PLANT. 

(if  the  plants  are  dioecious,  as  is  often  the  case  in 
mosses)  may  be  distinguished  by  the  expansion  of  the 
terminal  leaves,  thus  giving  the  ends  of  the  plants  some- 
thing of  the  appearance  of  inverted  umbrellas.  Also 
the  clusters  of  reddish-brown  antheridia  on  the  ends 
of  the  sterns  may  often  be  seen.  Archegonial  plants 
are  less  distinctly  marked.  They  have  the  leaves  so 
arranged  as  to  enclose  the  tip  of  the  stem,  and  their 
presence  is  often  indicated  by  the  development  of  the 
young  sporophytes  from  the  tips  of  some  leafy  shoots. 

The  sporophytes  may  develop  quite  early,  and  ripe 
spores  from  them  may  be  scattered  and  begin  a  new 
life-cycle  early  in  the  spring.  Specimens  of  antheridial 
and  archegonial  plants,  and  of  young  and  mature  spo- 
rophytes should  be  collected  and  preserved  in  alcohol 
or  formalin.  Plants  with  mature  sporophytes  should 
also  be  preserved  dry,  from  which  ripe  spores  can  be 
collected  and  sown  on  moist  earth  in  the  laboratory, 
since  the  young  stages  desired  can  be  easily  grown. 
Some  specimens  of  antheridial  and  archegonial  plants 
and  immature  capsules  should  be  prepared  for  sectioning. 
GROSS  STRUCTURE. 

Observe: 

1.  The  vertical  stem;  usually  unbranched. 

2.  The  leaves  which  are  borne  by  the  stem:  how  attached  to 
it. 

3.  The  rhizoids. 

4.  The  different  way  in  which  the  leaves  are  arranged  at  the 
tip  of  the  stalk. 

5.  On  some  plants,  the  sporophyte  with  slender  stalk,  seta 
bearing  the  capsule. 

6.  Draw. 


FUN  ARIA   HYGROMETRICA.  101 

MINUTE  STRUCTURE. 

I.  VEGETATIVE  STRUCTURE. 

Mount  and  examine  under  low  or  high  power,  as  may  be 
needed  to  demonstrate  the  structures  and  observe: 

1.  The  rhizoids;  their  structure  and  how  they  arise  from  the 
basal  end  of  the  stem.    Draw. 

2.  The  leaves. 

a.  Thickness  in  various  parts. 

b.  Specially  differentiated  cells  along  middle  of  leaf. 

c.  Prominent  chloroplastids  within  cells. 

d.  Draw,  showing  in  detail  the  different  kinds  of  cells  that 
compose  the  leaf. 

3.  The  stem. 

a.  How  stem  and  base  of  leaf  are  united. 

b.  Whether  stem  bears  chlorophyll. 

4.  The  protonema.     Examine  some  of  the  earth  in  which  the 
moss  plants  grew,  or  some  of  that  in  which  mature  moss 
spores  have  been  sown  some  weeks  previously.    If  the 
material  is  good,  it  should  show: 

a.  The  alga-like  structure  of  the  protonema;    cells  with 
chloroplastids;    method  of  branching.     Draw. 

b.  Buds  arising  from  protonema  and  gradually  developing 
into  the  leafy  shoots.     Draw  stages  illustrating  this 
development. 

II.  SEXUAL  REPRODUCTION. 

i.  Antheridium.  From  one  of  the  male  plants  carefully  re- 
move the  leaves,  allowing  at  least  a  part  of  the  antheridia 
to  remain  on  the  stem.  Observe: 

0.  The  position  and  general  arrangement  of  the  club- 
shaped  antheridia,  and 

b.  The  paraphyses  which  stand  among  them  and  extend 
above  them. 


102  A   MOSS  PLANT. 

c.  The  detailed  structure  of  a  single  antheridium.  When 
studying  fresh  material  it  is  often  possible  to  obtain 
antheridia  just  ripe  enough  to  allow  the  sperms  to 
escape  at  the  time  the  antheridia  are  mounted  in  water. 
If  possible,  obtain  such  a  preparation,  note  the  struc- 
ture and  behavior  of  the  sperms.  Note  where  and  how 
the  antheridium  opens.  Draw. 

2.  Archegonium.  From  female  plants  carefully  remove  the 
leaves,  and  locate  the  archegonia.     Observe: 

a.  The  attachment  of  the  archegonia;  the  structure  of  the 
paraphyses  associated  with  the  archegonia.    With  a 
single  archegonium  well  mounted  observe: 

b.  Its  general  form  and  structure,  much  as  in  liverworts; 
the  basal  stalk;  the  swollen  region,  venter;  the  elon- 
gated region,  the  neck,  with  a  central  row  of  neck  canal 
cells;  within  the  venter  a  spherical  cell,  the  egg;  imme- 
diately above  the  egg  and  below  the  neck  canal  cells 
the  -ventral  canal  cell. 

c.  Draw. 

d.  Try  to  find  archegonia  in  which  the  egg  is  fertilized, 
and  determine  how  the  sperm  obtained  entrance  to  the 

egg- 

e.  In  sections  of  old  archegonia  observe  the  early  divisions 
of  the  oospore  as  it  is  germinating. 

/.  Draw. 

III.  THE  SPOROPHYTE  AND  ASEXUAL  REPRODUCTION. 

1.  Observe  and  draw  a  young  sporophyte  just  emerging  from 
the  leaves. 

2.  Carefully  remove  the  young  sporophyte  by  pulling  it  out 
of  the  stalk  of  the  leafy  shoot,  and  observe: 

a.  The  elongated  stalk,  the  seta,  at  the  lower  end  of  which 
is  the  sharpened  foot  that  was  imbedded  within  the 
stalk  of  the  leafy  shoot. 


FUN  ARIA   HYGROMETRICA.  103 

b.  The  hood,  calyptra,  that  envelops  and  protects  the 
young  sporophyte.      Determine  its    relation    to   the 
archegonium. 

c.  Draw. 

3.  The  adult  sporophyte.     Observe: 

a.  The  elongated  stalk,  the  seta. 

b.  The  enlarged  tip,  the  capsule. 

c.  The  calyptra,  frequently  fallen  away  in  Funaria;  but  it 
may  be  found  in  some  species  at  maturity. 

d.  Draw,  showing  leafy  shoot  and  complete  sporophyte. 

e.  The  details  of  the  structure  of  the  capsule.     By  care- 
fully cutting  off  and  mounting  the  end  of  the  capsule 
observe: 

i.  The  operculum  or  lid,  covering  the  mouth,  and  early 
covered  by  the  calyptra. 

ii.  The  peristome,  fringing  the  mouth  inside,  composed 
of  projections,  the  teeth.  Some  mosses  have  two 
and  some  one  row  of  teeth.  Observe  the  number 
and  arrangement  of  the  teeth  and  the  differences  be- 
tween the  two  rows,  if  present, 
iii.  Draw. 

iv.  The  spores,  within  the  capsule. 

v.  By  means  of  prepared  sections  of  young  capsules, 
both  transverse  and  longitudinal,  study  the  position 
and  extent  of  sporogenous  and  sterile  tissues,  the 
stages  in  the  development  of  spores,  and  the  nature 
of  the  teeth. 

vi.  Draw. 

ANNOTATIONS. 

The  gametophyte  body  of  the  moss  is  distinctly  unlike 
that  of  the  liverworts  studied.  The  asexual  spores  of 
some  of  the  liverworts  in  the  earliest  stages  of  germination 


104  A   MOSS  PLANT. 

form  structures  not  unlike  the  moss  protonema,  but  al- 
most directly  they  pass  into  the  dorsiventral  liverwort 
body.  In  the  true  mosses  the  protonema  may  persist 
for  a  long  time  before  giving  rise  to  a  leafy  shoot.  But 
this  phase  of  the  gametophyte  is  purely  vegetative,  since 
it  produces  no  sexual  organs  and  consequently  cannot 
produce  a  sporophyte.  It  may  branch  and  extend 
itself,  thereby  increasing  in  vigor  and  probability  of 
producing  more  than  one  leafy  axis.  It  may  also  serve 
to  carry  the  plant  through  unfavorable  periods. 

With  the  development  of  the  leafy  shoot  from  the 
buds  on  the  protonema,  there  appear  structures  not 
equalled  in  complexity  by  the  gametophytes  of  the  liver- 
worts. The  upright  stem  supports  a  system  of  leaves 
that  are  radially  arranged,  thereby  exposing  the  chlorophyll 
to  the  light  in  a  better  way  than  has  yet  been  done.  At 
the  lower  end  of  the  stem  are  anchoring  organs,  the 
rhizoids.  It  may  be  that  these  absorb  materials  from 
the  earth  and  carry  them  to  the  stem,  through  which  by 
means  of  specialized  tissues  they  may  be  transported 
to  the  leaves.  The  stem  is  almost  entirely  relieved  of 
chlorophyll  work  and  is  given  over  mainly  to  the  work 
of  support,  its  form  and  structure  being  adapted  to  this 
function.  The  leaves  show  distinctly  differentiated  con- 
ducting tissues,  which  also  help  stiffen  the  leaf.  The 
margin  of  the  leaf  is  also  strengthened  in  some  cases. 

The  sexual  organs  are  borne  at  the  apex  of  the  gameto- 
phyte stalk  and  are  more  or  less  enclosed  by  the  paraphyses 
that  grow  among  them.  Mosses  may  be  monoecious  or 
dioecious.  The  oospore  begins  its  development  within 
the  venter  of  the  archegonium,  and  its  growth  stimulates 


FUN  ARIA   HYGROMETRICA  1 05 

the  venter  of  the  archegonium,  the  stalk,  and  a  part  of 
the  adjacent  tissues  of  the  axis  to  grow  so  as  to  form  a 
sheath  around  the  developing  sporophyte.  But  the  sporo- 
phyte  soon  outgrows  this  envelope  and  elongates  to  such 
an  extent  that  it  breaks  it  near  the  base.  As  the  sporo- 
phyte stalk  continues  to  grow,  i"s  end  carries  upward 
this  sheath  as  the  calyptra.  Meanwhile  the  lower  end 
of  the  sporophyte  becomes  imbedded  in  the  axis  of  the 
leafy  shoot,  from  which  it  absorbs  nourishment  for  the 
development  of  the  entire  sporophyte.  Thus  the  sporo- 
phyte is  parasitic  upon  the  gametophyte.  It  may  do  a 
little  in  manufacturing  food  by  means  of  chlorophyll,  for 
it  has  stomata  and  can  absorb  carbon  dioxid,  but  it 
must  get  its  water  and  salts  from  the  gametophyte. 

A  relatively  small  amount  of  tissue  is  sporogenous,  and 
there  exist  in  the  sterile  tissues  much  more  effective 
devices  for  protecting  sporogenous  tissues,  and  for  dis- 
tributing spores,  than  existed  in  the  liverworts.  It  is 
evident  that  in  this  entire  plant  we  have  quite  an  advance 
in  the  division  of  labor  among  the  parts  of  the  plant, 
and  a  consequent  increase  in  the  quality  and  quantity 
of  work  accomplished. 

It  will  be  remembered  that  in  the  Alga  Coleochate 
after  fertilization  of  the  egg  the  tissues  adjacent  to  it 
are  stimulated  to  growth  so  that  they  soon  enclose  the 
base  of  the  oogonium.  In  Riccia  after  fertilization  the 
tissues  continue  to  grow  about  and  nourish  the  develop- 
ing sporophyte.  About  the  base  of  the  archegonium  of 
Marchantia  there  grows  after  fertilization  an  extensive 
sheath  that  finally  completely  encloses  the  fully  formed 
sporophyte.  In  the  mosses,  when  the  fertilized  egg  has 


106  A  MOSS  PLANT. 

been  formed  some  of  the  gametophyte  structures  begin  an 
extensive  growth  that  bears  an  important  relation  to  the 
sporophyte.  This  stimulating  effect  upon  the  gameto- 
phyte through  fertilization  of  the  egg  is  significant,  and 
when  considering  higher  groups  there  will  be  occasion  to 
refer  to  the  facts  here  presented. 


THE    BRACKEN-FERN. 

Pteris  aquilina. 

PTERIDOPHYTES;  FILICALES;  FILICINE^l. 

PRELIMINARY. 

THIS  fern  is  general  in  its  distribution,  being  found 
under  a  variety  of  conditions.  The  leaves  stand  erect 
from  an  underground  stem,  and  branch  rather  exten- 
sively. They  sometimes  become  three  or  four  feet  long 
and  often  develop  in  such  numbers  as  to  produce  quite 
dense  growths.  The  underground  stem  is  sometimes 
many  feet  long,  and  may  have  leaves  arising  from  its 
tip  and  from  many  side  branches.  On  the  under  side 
of  leaflets  the  sporangia  appear,  being  protected  by  a 
fold  of  the  leaf  margin,  and  when  ripe  appear  reddish 
brown. 

Occasionally  one  may  find  the  gametophytes  on  damp 
earth  near  the  adult  plants.  They  may  range  in  size 
from  one  or  two  millimeters  to  one  or  two  centimeters 
across.  They  are  irregularly  heart-shaped  and  are  held 
close  to  the  soil  by  a  system  of  rhizoids  that  arise  from 
the  lower  surface  of  the  gametophyte  body.  In  some 
cases  a  primary  leaf  of  a  young  sporophyte  may  be  seen 
107 


108  THE  BRACKEN -FERN. 

arising  apparently  from  the  notch  at  the  forward  end 
of  the  gametophyte. 

The  following  materials  should  be  collected:  the  un- 
derground stem  or  rhizome  with  the  roots  that  grow 
from  it,  care  being  taken  not  to  tear  away  the  fine  roots; 
a  piece  of  young  rhizome  suitable  for  sections,  the  latter, 
and  a  good  supply  of  roots  with  their  tips  uninjured, 
being  preserved  in  formalin  or  alcohol  and  a  few  young 
roots  preserved  for  microtome  sectioning;  a  supply  of 
leaves,  with  and  without  sporangia,  some  being  pressed, 
some  being  preserved  in  alcohol  or  formalin,  and  some 
pieces  of  leaves  bearing  sporangia  being  prepared  for 
sectioning;  a  supply  of  ripe  sporangia  with  their  spores, 
preserved  dry. 

About  six  weeks  before  the  laboratory  work  is  to  be 
begun  some  of  the  spores  should  be  sown  on  damp  earth 
or  sand  in  a  dish  that  should  be  kept  covered.  This  sow- 
ing will  usually  furnish  a  supply  of  gametophytes  for  lab- 
oratory study. 

Pteris  cretica  and  P.  cristata,  common  greenhouse  ferns, 
will  serve  well  for  this  work,  as  will  also  the  maiden- 
hair fern,  Adiantum  pedatum.  Numerous  other  ferns 
will  furnish  excellent  material  in  case  none  of  the  above 
can  be  obtained. 

GENERAL  STRUCTURE. 

I.  THE  RHIZOME  AND  ROOTS.     Observe: 

1.  The  flattened  dorsi ventral  stem,  the  upper  and  lower  por- 
tions being  divided  by  prominent  ridges. 

2.  The  roots  arising  from  the  ventral  surface  and  sides. 

3.  The  roots,  each  (if  uninjured  )  with  a  small  root-cap  at  its 
tip. 


PTERIS  AQUILINA.  109 

4.  The  nodes  and  internod.es  of  the  stem;  the  nodes  are  indi- 
cated by  the  growth  of  a  leaf  at  each,  alternately  on  the 
right  and  left  sides:  the  intervals  between  the  nodes  are  the 
internodes. 

5.  Draw. 

II.  THE  LEAF.     Observe: 

1.  The  leaf -stalk,  or  petiole,  arising  from  the  rhizome  and  fre- 
quently miscalled  the  "stem";    its  strength  and  general 
appearance. 

2.  The  system  of  branching. 

3.  The  leaf  blades,  or  leaflets. 

4.  The  arrangement  of  veins  in  the  blades,  -venation. 

5.  The  sporangia,  and  the  folded  edge  of  the  leaflet  that 
protects  them.     When  sporangia   grow  in  clusters  each 
cluster  is  called  a  sorus  (pi.  sori).    When  there  is  an  epi- 
dermal outgrowth  above  a  sorus  it  is  called  an  indusium. 
In  Pteris  the  folded  leaf  margin  is  a  false  indusium. 

6.  Draw. 

MINUTE  STRUCTURE. 
I.  THE  STEM. 

Make  a  thin  transverse  section  of  the  stem  and  study  the 
general  regions  by  means  of  the  low  power,  and  the  cell 
structure  by  means  of  the  high  power.  Observe: 

1.  Epidermal  region,  consisting  of  a  single  layer  of  cells. 

2.  The  sclerenchyma,  the  heavy-walled  strengthening  tissue 
beneath  the  epidermis. 

3.  Within  this  outer  layer  of  sclerenchyma,  the  irregularly 
semicircular  fibrovascular  region  enclosed  by  a  layer  of 
cells,  the  bundle-sheath.    Within  the  bundle  is  composed 
of  very  heavy- walled  cells  (xylem),  and  others  (the  phloem) 
with  much  thinner  walls.     Study  xylem  and  phloem  cells 
and  observe  their  distribution  with  reference  to  one  an- 


no  THE  BRACKEN-FERN. 

other.     Enclosed  by  the  fibrovascular  region  is  a  mass  of 
axial  sclerenchyma  whose  cells  resemble  those  seen  in  2. 

4.  Diagram  the  entire  section  and  draw  in  detail  a  narrow 
strip  across  it,  so  as  to  show  all  the  kinds  of  tissues.    Make 
a  longitudinal  section  of  the  stem,  and  identify: 

5.  The  various  regions  observed  in  the  cross-section.     Draw. 

II.  THE  ROOT. 

Make  a  transverse  section  of  one  of  the  larger  roots,  study 
it,  and  make  a  diagram,  showing: 

1.  The  epidermal  region. 

2.  The  parenchyma,  composed  of  cells  of  approximately  equal 
dimensions. 

3.  The  sclerenchyma,  resembling  that  of  the  stem. 

4.  The  fibrovascular   bundle  and  its  bundle-sheath.     No- 
tice the  starch  stored  in  the  above  tissues.     Select  some 
roots  with  uninjured  tips  and  make  longitudinal  sections 
of  the  tip.1     Observe: 

5.  The  layers  of  the  root-cap. 

6.  Under  the  root-cap  in  the  median  section  a  large  triangular 
cell,  apex  inward,  the  apical  cell.     Notice  that  the  cells 
adjacent  to  the  inner  faces  of  the  apical  cell  have  evidently 
been  derived  from  it  by  partitions  parallel  to  its  faces. 

7.  Draw  the  tip  of  the  root,  including  the  apical  cell  and  the 
root-cap. 

III.  THE  LEAVES. 

i.  Epidermis.  Lift  the  epidermis  of  the  lower  surface  with 
the  point  of  a  needle  or  scalpel,  seize  it  with  fine  forceps 
and  strip  off  a  small  piece,  mount  it  with  the  outer  sur- 
face upward,  and  observe: 

a.  The  very  irregular  epidermal  cells  and  the  way  they 
dovetail  into  one  another. 

1  The  best  results  will  be  obtained  if  .serial  microtome  sections  are 
at  hand. 


PTERIS  AQUILINA.  Ill 

b.  Here  and  there  narrow  slit-like  stomata,  each  consisting 
of  an  opening  bounded  by  two  crescentic  cells,  the 
guard-cells. 

c.  Along  certain  lines  (over  the  veins)  the  different  shape 
of  the  epidermal  cells. 

d.  The  chloroplasts,  especially  in  the  guard-cells. 

e.  Make  a  drawing  showing  these  points. 

/.  Examine  in  the  same  way  the  epidermis  of  the  upper 

surface  of  a  leaflet;   note  the  absence  of  stomata. 
2.  Make  a  transverse  section  of  a  leaflet,1  mount,  and  observe: 

a.  The  upper  and  lower  epidermis;  the  sections  of  stomata 
appearing  in  the  latter.     Note  also   the   substomatal 
chamber  within  the  green  tissue. 

b.  The  mesophyll,  the  chlorophyll-bearing  tissue. 

c.  The  veins. 

d.  Draw. 

IV.  SPORANGIA  AND  SPORES. 

From  a  ripe  sorus  remove  and  mount  some  sporangia.     In 
a  perfect  specimen  observe: 

1.  The  stalk  on  which  it  was  borne. 

2.  The  form  of  the  main  body  or  spore-case. 

a.  On  one  edge  note  the  row  of  heavy-walled  cells,  the 
annulus.    Where  are  its  ends? 

b.  The  cells  that  form  the  rest  of  the  wall. 

3.  The  spores. 

4.  Draw. 

5.  Place  on  the  slide  some  sporangia  that  have  been  moistened 
in  water,  allow  them  to  become  dry  as  they  are  observed 
with  the  low  power,  and  determine  just  how  the  sporan- 
gium acts  in  expelling  spores.     Make  diagrams  illustra- 
ting the  changes  in  position  of  the  annulus  and  the  side 
walls  during  this  process. 

1  These  leaf  sections  will  be  most  satisfactory  if  made  from  material 
imbedded  in  paraffin. 


112  THE  BRACKEN-FERN'. 

If  good  microtome  sections  of  young  sori  can  be  had,  study 
and  draw,  showing  the  development  of  the  sporangia,  observ- 
ing the  following  stages: 

6.  The  young  stalk  with  cell  divisions  at  right  angles  to  its 
long  axis. 

7.  An  oblique  division  forming  an  apical  cell. 

8.  The  primary  wall  cells  surrounding  the  single  archesporial 
cell. 

9.  Completed  wall  cells,  surrounding  sporogenous  cells. 

10.  Sporangia  containing  spore  mother-cells,  and  others  with 

spores. 
V.  THE  GAMETOPHYTE  AND  SEXUAL  REPRODUCTION. 

1.  The  gametophyte  body.     Examine  the  soil  or  brick  upon 
which  spores  were  sown  some  three  or  four  weeks  pre- 
viously.    Observe: 

a.  The  green  coating  given  by  the  young  gametophytes 
(prothallia)  developing  from  the  spores.     Mount  some 
of  the   material   and   study  the   development   of  the 
gametophyte,  observing  the  following  stages: 

b.  Spores  just  beginning  to  germinate,  showing  the  pro- 
tonemal  or  filamentous  structure,  and  the  first  rhizoid. 
Draw. 

c.  Specimens  in  which  the  filament  begins  to  broaden  by 

means  of  longitudinal  and  oblique  cell-walls,  as  well  as 
by  the  transverse  ones  that  first  appeared.     Such  stages 
should  show  the  early  appearance  of  the  apical  cell; 
also  the  formation  of  rhizoids.     Draw. 
In  material  six  to  eight  weeks  old  examine: 

d.  Fully  formed  gametophytes,  showing  the  characteristic 
heart-shaped  body,  the  deep  apical  notch,  the  rhizoids 
on  the  under  side  of  the  dorsiventral  body.     Diagram 
the  body,  and  draw  a  few  cells  in  detail. 

2.  Sex  organs  and  gametes. 
a.  Antheridia. 


PTERIS  AQUILINA.  113 

On  rather  young  gametophytes  antheridia  may  often 
be  seen  extending  outward  from  almost  any  of  the 
marginal  cells;  on  old  gametophytes  they  do  not  grow 
in  this  position,  but  on  a  definite  part  of  the  under  sur- 
face of  the  body.  They  may  be  most  easily  studied  on 
young  gametophytes.  Locate  good  antheridia  in  such 
position  as  to  be  seen  from  a  side  view.  Study, 
observing: 
i.  The  short  antheridial  stalk,  and  how  it  arises  from 

the  body. 

ii.  The  wall  cells;  note  that  the  tip  cell  is  arranged  so 
as  to  make  a  ready  opening  for  the  escape  of  sperms 
when  ripe. 

iii.  The  centrally  placed  sperms  or  sperm  mother-cells, 
iv.  Draw. 

By  mounting  in  water  some  rather  dry  gametophytes 
that  are  producing  antheridia,  it  will  often  be  possible 
to  obtain  sperms  in  the  process  of  escaping.     Make 
such  a  mount,  and  observe: 
v.  The  form  and  movement  of  the  sperms.    Stain  with 

iodin,  and  observe: 
vi.  The  cilia. 

vii.  The  body  of  the  sperm, 
viii.  Draw. 
b.  Archegonia. 

Mount  fully  formed  gametophytes  with  the  ventral 
surface  uppermost,  and  observe: 

i.  The  archegonial  necks  protruding  from  the  surface, 
and  curved  away  from  the  notch.  Sometimes  the 
opening  into  the  neck  can  be  seen.  Draw.  By 
means  of  microtome  sections  cut  perpendicular  to 
the  surface  and  along  the  longitudinal  axis  of  the 
gametophyte,  study  the  structure  of  the  archegonium, 
observing: 


114  THE  BRACKEN-FERN. 

ii.  The  imbedded  venter,  from  which 
iii.  The  recurved  neck  extends, 
iv.  The  egg,  ventral  canal,  and  neck  canal  cells, 
v.  Draw. 

VI.  THE  YOUNG  SPOROPHYTE. 

By  means  of  sections  made  as  for  2.  b.  ii.  study  early  stages 
in  the  development  of  the  sporophyte.  Observe: 

1.  Recently  fertilized  eggs,  in  which  the  first  division  wall 
has  appeared.     Note  its  direction  and  how  it  divides  the 
oospore.    Draw. 

2.  The  direction  of  the  second  division  walls,  and  the  result- 
ing quadrants.     Each  of  these  quadrants  forms  a  definite 
organ  of  the  young  sporophyte  embryo,  foot,  stem,  leaf,  or 
root.     Draw. 

3.  Some  older  sporophyte  embryos  in  which  some  of  the  em- 
bryonic organs  are  discernible.     Draw. 

4.  With  some  fresh  material  search  for  specimens  in  which 
the  first  leaf  of  the  young  sporophyte  is  emerging  from  the 
notch  of  the  gametophyte,  while  the  real  stem  is  beginning 
to  grow  downward,  and  the  foot  still  holds  the  young  plant 
to  the  old  gametophyte.     Draw. 

ANNOTATIONS. 

A  striking  difference  between  Pteris  and  any  Bryophyte 
studied  is  seen  in  the  fact  that  in  ferns  the  mature  gameto- 
phyte and  sporophyte  generations  are  able  to  live  inde- 
pendent of  one  another.  Each  has  organs  relating  it  to  the 
surrounding  medium,  and  each  has  chlorophyll  by  means 
of  which  it  can  manufacture  food  from  what  it  can  absorb. 
The  gametophyte  is  for  a  brief  time  dependent  upon 
food  stored  in  the  spore  that  forms  it,  and  the  sporophyte 


PTERIS  AQUILINA.  115 

foot  absorbs  from  the  gametophyte  the  nourishment 
for  the  embryo  sporophyte,  but  each  soon  becomes 
able  to  provide  for  itself. 

The  gametophyte  is  not  so  large  or  complex  a  structure 
as  that  of  the  Bryophytes.  It  is  dorsiventral  and  in 
several  ways  greatly  resembles  the  gametophyte  of 
Anthoceros.  In  the  way  in  which  it  develops  it  also 
shows  striking  resemblance  to  Bryophyte  gametophytes. 
The  antheridia,  which  are  usually  formed  on  the  basal  part 
of  the  gametophyte,  are  outgrowths  from  surface  cells, 
and  are  not  so  complex  as  were  those  found  in  Bryo- 
phytes. The  sperms  are  spiral,  bear  many  cilia,  and  move 
with  great  rapidity.  The  archegonia  have  their  venters 
deeply  embedded  within  the  gametophyte,  but  their 
necks  protrude  and  are  so  directed  that  when  the  tips 
open  they  are  favorably  placed  to  admit  the  sperms. 

The  first  division  of  the  oospore  is  effected  by  means 
of  a  wall  that  runs  at  right  angles  to  the  surface  of  the 
gametophyte  and  almost  parallel  with  the  long  axis  of 
the  archegonium.  The  next  wall  runs  at  right  angles 
to  the  first,  and  the  two  divide  the  oospore  into  four 
quadrants,  an  outer  and  inner  anterior,  and  an  outer 
and  inner  posterior.  The  outer  anterior  produces  the 
first  leaf;  the  inner  anterior  produces  the  first  stem; 
the  primary  root  is  produced  by  the  outer  posterior,  and 
the  inner  posterior  produces  the  foot.  The  embryonic 
foot  and  embryonic  root  disappear,  the  real  stem  becom- 
ing the  rhizome  from  which  the  secondary  roots  arise. 
The  primary  leaf  is  also  transient,  new  and  larger  leaves 
being  formed  annually  from  the  rhizome.  It  is  evident 
that  this  definiteness  in  the  origin  of  organs  from  the 


Il6  TEE  BRACKEN-FERN. 

parts  of  the  oospore  is  a  marked  advance  over  Bryophytic 
conditions. 

The  sporophyte,  which  in  Bryophytes  is  always  para- 
sitic, is  here  a  prominent  structure  bearing  extensive 
leaf  surfaces,  thereby  exposing  much  chlorophyll  to 
the  light.  This  increase  in  chlorophyll  work  is  neces- 
sarily accompanied  by  an  increase  in  mechanical  and 
conducting  tisues.  The  conducting  system  is  far  superior 
to  anything  seen  in  Bryophytes,  as  is  also  the  mechanical 
system.  The  leaf-stalk  supports  the  chlorophyll  tissue, 
the  real  stem  being  underground,  where  it  serves  as  the 
axis  for  the  secondary  root  system,  and  also  serves  as  a 
storage  region  for  surplus  food. 

For  the  development  of  the  organs  of  the  plant, 
gametophyte,  root,  stem,  etc.,  growth  is  localized;  and 
in  each  such  locality  there  is  present  a  specialized  cell, 
the  apical  cell,  from  whose  faces  new  cells  are  cut  off 
by  partition-walls.  After  each  division  it  enlarges,  and 
repeats  the  process  on  another  face.  Adjacent  cells 
also  divide  and  grow,  and  this  may  occur  anywhere. 
But  the  apical  cell  is  very  active  in  division,  and  thus 
marks  a  region  of  growth. 

Sporangia  arise  from  a  single  surface  cell,  which  is 
indicated  by  saying  that  this  plant  is  kptosporangiate. 
The  sporangia  are  stalked  and  have  a  special  structure, 
the  annulus,  for  the  distribution  of  spores. 

This  plant  exemplifies  well  the  order  Filicales,  the 
true  ferns,  one  of  the  chief  orders  of  Pteridophytes, 


"SCOURING-RUSH,"  OR  "HORSETAIL." 

Equisetum  arvense. 

PTERIDOPHYTES;  EQUISETALES;  EQUISETINE^. 

PRELIMINARY. 

THIS  plant  is  selected  as  a  representative  of  a  subdi- 
vision of  the  Pteridophytes,  the  Equisetales,  in  which  there 
are  about  twenty-five  living  species,  all  belonging  to  one 
genus.  Other  species  may  be  selected  for  study,  but 
the  one  named  will  be  found  most  often  in  many  localities. 
It  grows  on  shady  hillsides,  along  railway  tracks,  and 
sometimes  in  open  fields.  It  may  be  found  along  the 
banks  of  ponds  and  streams,  but  in  such  places  other 
species  of  Equisetum  are  more  likely  to  be  found. 

The  pale  reddish-yellow  spore-bearing  branches  appear 
early  in  the  spring,  usually  the  latter  part  of  March 
or  April.  They  are  straight  unbranched  shoots,  from 
three  to  twelve  inches  in  height,  and  bear  cone-like 
structures  at  their  tips.  Near  these  achlorous  shoots 
and  arising  from  the  same  underground  stems  will 
be  seen  the  branched  green  shoots.  These  become 
much  more  prominent  as  the  spore-bearing  shoots  dis- 
appear. In  other  species  than  Equisetum  arvense  the 
spores  are  borne  by  single  tall  unbranched  green  shoots. 
"7 


Ii8  " SCOURING-RUSH,"  OR   "HORSETAIL." 

Good  material  of  root-stocks  and  both  kinds  of  aerial 
shoots  should  be  collected  and  preserved,  some  by 
pressing  and  drying,  and  some,  especially  spore-bearing 
shoots,  in  alcohol  or  formalin.  Fresh  material,  if  obtain- 
able, should  be  used. 

LABORATORY  WORK. 
GROSS  STRUCTURE. 

I.  THE  SPORE-BEARING  SHOOT.     Observe: 

1.  The  straight  jointed  stem. 

2.  The  circle  of  leaves  at  each  joint  (node). 

3.  The  structure  of  the  node  as  seen  when  a  stem  is  broken 
at  that  point. 

4.  The    terminal    cone,    composed    of    small   spore-bearing 
leaves  (sporophylls)  arranged  in  regular  order. 

5.  Draw. 

II.  The  GREEN  SHOOTS.    Observe: 

1.  Mode  of  branching. 

2.  Similarity  in  structure  of  the  main  axis  and  its  branches 
to  that  of  the  stem  which  bears  the  cone. 

3.  Draw  two  or  three  internodes. 

III.  RHIZOME. 

Observe  how  the  leaves  and  roots  arise  from  it.  Show  this 
by  a  sketch. 

MINUTE  STRUCTURE. 
I.  THE  AERIAL  STEM. 

Make  a  cross-section  between  the  nodes  of  a  spore-bearing 
shoot  and  of  a  green  shoot;  mount  under  one  cover  and  com- 
pare as  to: 

1.  The  general  outline  of  the  cross-section. 

2.  The  ridges  and  furrows  along  the  outer  surface. 


EQUISETVM  ARVENSE.  lip 

3.  The  location  of  the  chlorophyll-bearing  cells. 

4.  The  stomata   and   their  location.     (Compare   with  sur- 
face view.) 

5.  The  location  of  vascular  bundles. 

6.  Draw. 

II.  THE  SPOROPHYLLS. 

Remove  a  few  of  the  sporophylls,  and  lay  in  water  so  that 
they  may  be  seen  from  different  directions.     Observe: 

1.  The  form  of  the  outer  parts  of  the  sporophylls. 

2.  The  central  stalk. 

3.  The  number  and  position  of  the  sporangia. 

4.  Draw. 

Tear  open  some  of  the  sporangia,  mount  and  observe  under 
the  microscope: 

5.  The  spores,  whose  outer  wall  forms: 

6.  The  elaters.     Note  the  position  of  the  elaters  when  the 
spores  are  moist.     Allow  some  spores  to  dry  on  a  slide 
while  watching  them,  and  note  the  position  and  behavior 
of  the  elaters  as  they  become  dry. 

7.  Draw. 

ANNOTATIONS. 

Equisetum  arvense  shows  at  least  two  features  not  yet 
seen  in  any  of  the  plants  studied,  although  one  of  these 
exists  in  some  of  the  true  ferns.  First,  the  spore-bearing 
shoot  is  separated  from  the  green  vegetative  shoot;  and 
secondly,  the  sporophylls  upon  this  spore-bearing  shoot 
are  distinctly  unlike  foliage  leaves,  as  we  commonly 
know  them,  and  are  gathered  into  a  compact  cone- like 
cluster.  All  the  chlorophyll  work  is  done  by  the  branched 
shoots,  the  leaves  doing  none  and  apparently  serving 


120  "SCOU RING-RUSH,"   OR   "HORSETAIL." 

merely  to  stiffen  the  nodes  and  to  protect  the  basal  grow- 
ing regions  of  each  internode. 

The  stems  are  jointed,  tubular,  and  ridged,  the  chlor- 
ophyll appearing  within  the  ridges,  and  the  stomata 
along  their  slopes.  The  stems  also  contain  much  silica 
which  makes  them  gritty. 

Surplus  food  is  stored  in  the  rhizome,  and  is  used 
partially  or  wholly  as  nourishment  for  the  sporiferous 
stalk  early  in  the  succeeding  season. 

In  the  groups  of  sporangia  on  the  sporophyll  many 
spores  are  borne.  Each  spore  is  covered  as  it  develops 
by  a  special  outer  coat  which  cracks  at  maturity  in  a 
spiral  fashion  and  so  forms  the  elaters,  not  at  all  the 
morphological  equivalents  of  elaters  of  liverworts.  As 
the  spore  becomes  dry  the  elaters  straighten,  and  in 
doing  so  jerk  the  spores  about  from  place  to  place. 
Becoming  entangled,  they  may  also  hold  several  spores 
together  for  a  tune. 

The  spores  produce  gametophytes,  each  of  which 
bears  but  one  kind  of  sex-organ,  i.e.  is  direcious.  Since 
elaters  hold  the  spores  in  masses,  one  kind  of  sex-organ 
is  more  likely  to  be  formed  in  the  vicinity  of  the  other 
than  would  be  true  if  the  spores  were  scattered  singly.1 

Equisetums  were  far  more  abundant  and  luxuriant  for- 
merly than  now.  Fossil  remains  show  that  during  the 
coal  ages  some  genera  of  the  order  were  often  large  trees 
that  composed  a  prominent  part  of  the  vegetation.  These 
highly  specialized  forms  have  ceased  to  exist  and  are 
now  represented  only  by  their  fossils  and  by  their  lowly 

1  If  fresh  spores  may  be  had,  it  will  be  possible  to  study  the  gameto- 
phytes and  sex-organs.  The  spores  germinate  quite  readily  and  must 
be  used  soon  after  being  gathered,  else  they  lose  their  power  to  germinate. 


EQUISETUM  ARVENSE.  121 

kin,  the  genus  Equisetum  with  about  twenty-five  living 
species.  The  species  of  to-day  are  more  simple  in  struc- 
ture than  some  of  those  of  geological  ages.  The  order 
is  in  its  old  age  and  has  almost  disappeared.1 

1  Read  on  Fossil  Equisetums  in  Seward's  "Fossil  Plants"  or  other 
text-books  that  describe  them. 


THE  "CLUB-MOSS." 

Selaginella  sp. 

PTERTDOPHYTES;     LYCOPODIALES ;    SELAGINELLACE^. 

PRELIMINARY. 

IN  the  Lycopodiales,  the  order  to  which  this  plant 
belongs,  there  are  only  a  few  genera.  These  bear  much 
general  resemblance  to  one  another,  although  they  are 
quite  unlike  in  several  important  details.  Selaginella 
is  one  of  the  few  living  plants  that  are  intermediate  in 
certain  characters  between  other  Pteridophytes  and  the 
lowest  Spermatophytes.  Most  of  its  species  are  found 
in  the  warmer  temperate  regions  and  the  tropics,  although 
a  few  inhabit  the  colder  temperate  regions.  Some  spe- 
cies are  commonly  grown  in  greenhouses,  where  the  fruit- 
ing spikes  may  often  be  found  and  collected  for  class  use. 
Fresh  material  will  be  much  better  for  study,  but  the  plant 
retains  its  characters  in  alcohol  and  formalin,  and  may 
thus  be  kept  indefinitely  for  class  use.  If  S.  rupestris 
can  be  obtained  it  will  be  found  highly  satisfactory. 


SELAGINELLA   SP.  123 

LABORATORY  WORK. 
GROSS  STRUCTURE. 

I.  THE  VEGETATIVE  BODY. 

With  a  good  branch  as  a  specimen,  observe: 

1.  The  position  in  which  the  stem  grew. 

2.  Position  of  leaves. 

3.  The  number  of  rows  of  leaves,  their  relative  size,  and  their 
distribution  on  the  stem.     Note  how  the  size  and  position 
of  leaves  are  adapted  so  that  all  may  have  sufficient  ex- 
posure to  light. 

4.  Aerial  roots,   coming  from  the  stem  as  branches  and 
descending  to  the  soil.     Draw. 

II.  THE  REPRODUCTIVE  BODY. 

At  the  tips  of  some  branches  the  sporophylls  form  a  close 
cluster,  known  also  as  a  spike  or  a  strobilus.     Observe: 

1.  The  number  of  rows  of  sporophylls. 

2.  The  arrangement  of  the  sporophylls. 

3.  Through  some  of  the  sporophylls,  the  sporangia,  appear- 
ing as  yellow  or  red  dots. 

4.  Draw. 

MINUTE  STRUCTURE. 

I.  THE  LEAF. 

Mount  an  entire  leaf,  and  observe: 

1.  General  form  of  cells  in  the  midrib,  the  margin,  and  the 
body.     Examine  these  in  detail,  particularly  the  cells  of 
the  main  part  of  the  leaf  and  the  peculiar  plastids  they 
enclose. 

2.  Draw. 

II.  THE  STEM. 

By  means  of  a  cross-section  of  the  stem  observe: 


124  THE   "CLUB-MOSS." 

1.  The  outermost  (epidermal)  layer  of  cells,  and  the  thick 
cuticle  which  is  the  outer  layer  of  its  surface  walls. 

2.  The  centrally  placed  vascular  bundle  region.     Note  the 
distribution  of  xylem  and  phloem  and  compare  with  the 
vascular  bundle  of  Pteris. 

3.  Draw  a  sector  of  the  section. 

III.  ASEXUAL  REPRODUCTION. 

Some  sporophylls  bear  sporangia  which  contain  many  small 
spores;  others  bear  sporangia  in  which  large  spores  are  formed. 
The  two  kinds  are  sometimes  found  in  the  same  strobilus. 
Remove  and  mount  several  sporophylls,  and  observe: 

1.  The  sporangium  on  each  one.     Make  a  drawing  of  a  good 
specimen. 

2.  Open  the  walls  of  the  sporangium  and  observe  the  spores. 

3.  Compare  the  two  kinds  of  sporangia  as   to  color,  form, 
and  size,  and  draw  both  kinds. 

4.  Determine  the  number  of  megaspores  (large  spores)  pro- 
duced in  a  sporangium.1 

5.  Mount  microspores  and  megaspores  so  that  both  can  be 
seen  in  one  view  by  use  of  the  low  power,  and  make  draw- 
ing showing  their  relative  size  and  similarity  of  form. 

IV.  SEXUAL  REPRODUCTION.2 

i.  The  male  gametophyte.    In  a  section  through  the  wall  of 
a  microspore  that  has  germinated  observe; 

1  The  number  of  microspores  (small  spores)  produced  in  a  sporangium 
is  so  great  that  it  will   not  be  possible    readily   to  determine   their 
number. 

2  It  is  very  difficult  to  obtain  sections  that  will  show  satisfactorily 
the  gametophytes  of  Selaginella.     Directions  for  making  such  sections 
may  be  found  in  Chamberlain's  "Methods  in  Plant  Histology,"  pp.  in— 
113.     If  sections  of  the  gametophytes  of  Marsilia  can  be  had,  they  will 
serve  well  in  place  of  those  of  Selaginella.     Usually  it  will  be  found  much 
more  satisfactory  if  there  are  supplied  prepared  sections  of  Marsilia  or 
Selaginella  for  this  work.     The  gametophyte   development  is  not  the 
same  in  the  two  genera,  but  the  Selaginella  outline  can  be  readily  ad- 
justed to  the  study  of  Marsilia. 


SELAGINELLA   SP.  125 

a.  The  cells  formed  just  within  the  spore  wall  and  that 
separate  it  from: 

b.  A  centrally  placed  cell,  which  later  divides,  thus  form- 
ing the  mother-cells  that  in  turn  form  the  sperms.1 

c.  Draw. 

2.  The   female   gametophyte.     By  studying  a  section  of  a 
germinating  megaspore  observe: 

a.  The  space  enclosed  by  the  megaspore  wall  partially 
filled  at  its  apical  end  by  female  gametophyte  tissue. 

b.  The  basal  part  containing  vacuoles,  or  granular  food 
substances,  or  both. 

c.  The  archegonia  developed  on  the  part  of  the  gameto- 
phyte exposed  by  the  rupture  of  the  spore  wall. 

d.  Draw. 

In  some  sections  it  may  be  that  eggs  have  been  fertilized 
and  stages  in  the  development  of  the  sporophyte  embryo  can 
be  seen.  If  so,  note  the  following  stages: 

e.  The  first  division-wall  of  the  oospore. 

/.  The  elongation  of  the  outermost  of  the  two  cells 
formed  by  the  first  division  of  the  oospore.  This 
elongated  cell  is  the  suspensor  and  serves  to  push 
the  other  cell  (embryo-cell)  into  the  female  gameto- 
phyte that  nourishes  the  embyro  as  it  develops. 

g.  A  specimen  in  which  embryonic  leaves,  stem,  and  root 
can  be  distinguished. 

h.  A  specimen  in  which  the  young  sporophyte  plant  is 
emerging  through  the  megaspore  wall. 

i.  Draw,  illustrating  the  various  stages  seen. 

1  With  Marsilia  it  is  comparatively  easy  to  obtain  living  sperms  by 
placing  the  dried  sporocarps  in  water.  After  a  day  or  two  the  micro- 
sporangia  and  spores  will  be  pushed  out  of  the  sporocarp  and  the  sperms 
will  escape  from  the  male  gametophytes  produced  within  the  micro- 
spore  walls. 


126  THE   "CLUB-MOSS: 


ANNOTATIONS. 

In  general  appearance  Selaginella  is  more  like  higher 
plants  than  any  Pteridophyte  yet  studied,  and  this  general 
resemblance  is  borne  out  in  detail  in  most  of  its  struc- 
tures. The  stem  is  not  so  complex  as  in  some  of  the  true 
ferns,  but  has  similar  concentric  vascular  bundles.  The 
horizontal  stem  bears  four  rows  of  leaves,  those  of  the 
two  uppermost  rows  being  small  and  so  arranged  as 
not  to  shade  the  larger  lower  ones.  The  lower  leaves 
are  twisted  on  their  petioles  so  as  to  expose  their  flat 
surfaces  to  the  light. 

The  aerial  roots  serve  to  support  the  stem  from  which 
they  come,  and  also  to  absorb  nourishment  from  the 
earth. 

In  the  Pteridophyte  groups  previously  studied  the 
asexual  spores  are  all  of  one  kind.  In  Pteris  it  was 
seen  that  any  spore  possessed  the  power  of  producing  a 
gametophyte  that  could  form  both  kinds  of  sex-organs 
and  gametes.  It  was  observed  in  that  connection  that 
a  small  or  poorly  nourished  gametophyte  produced 
antheridia  and  no  archegonia.  In  those  ferns  that 
have  only  one  kind  of  asexual  spore  (homosporous 
ferns)  the  question  of  nutrition  seems  to  determine 
whether  a  gametophyte  can  produce  both  sex-organs. 
In  Selaginella,  as  in  all  higher  plants,  there  are  two 
kinds  of  asexual  spores,  each  of  which  produces  a  certain 
kind  of  gametophyte.  The  microspore  upon  germina- 
tion produces  a  male  gametophyte,  which  in  turn  bears 
the  male  sex-organ  containing  male  gametes.  The 
megaspore  produces  the  female  gametophyte  on  which 


SELACINELLA    SP.  127 

the  archegonium  with  its  egg  is  formed.  These  spores 
are  produced  in  specialized  sporangia  on  specialized 
sporophylls.  The  sporophylls  are  gathered  into  strobili 
or  cones. 

A  difficulty  for  the  beginning  student  in  studying 
plants  with  two  kinds  of  asexual  spores  (heteros porous 
plants)  often  arises  from  the  fact  that  the  gametophytes 
are  greatly  reduced  in  size  and  are  almost  entirely  enclosed 
by  the  walls  of  the  spores  that  produce  them.  It  is 
usually  impossible  by  superficial  observation  to  determine 
whether  the  structure  is  an  asexual  spore,  or  a  gametophyte 
enclosed  by  an  old  asexual  spore-wall.  It  must  always 
be  kept  clearly  in  mind  that  the  spores  which  produce 
these  gametophytes  are  neither  male  nor  female,  but 
asexual  spores.  Spores  are  called  asexual  with  reference 
to  the  way  in  which  they  are  formed,  not  with  reference 
to  what  they  produce  when  they  germinate. 

After  fertilization  has  taken  place,  the  oospore  begins 
its  germination  by  means  of  a  wall  that  cuts  it  into  two 
cells,  one  of  which  elongates  and  forms  the  suspensor. 
This  pushes  the  other  one  down  into  the  female  game- 
tophyte tissue,  where  it  grows  at  the  expense  of  food 
absorbed  from  the  gametophyte  and  soon  forms  the 
embryo,  which  early  shows  the  rudiments  of  foot,  root, 
stem,  and  leaves.  The  latter  three  organs  gradually 
break  through  and  emerge  from  the  female  gametophyte 
and  the  plant  soon  becomes  independent.  All  these  proc- 
esses except  the  last  often  occur  before  the  megaspore 
has  even  escaped  from  the  sporangium.  If  before  the 
embryo  emerged  it  had  become  dormant  while  enclosed 
in  the  female  gametophyte,  and  the  wall  of  the  megaspo- 


128  THE   "CLUB-MOSS." 

rangium  had  developed  so  as  to  form  a  firm  covering  for 
the  gametophyte  and  embryo,  we  should  have  a  seed,  the 
characteristic  structure  of  the  next  great  group.1 

It  is  by  no  means  certain  that  seed-plants  originated 
from  ancestors  like  Selaginetta.  Nevertheless  the  resem- 
blance between  it  and  the  great  group,  Angiosperms,  is 
striking  and  too  significant  to  be  overlooked. 

1  Examine  text  illustrations  of  Selaginella,  and  also  those  by  Miss 
Florence  M.  Lyon  on  "A  Study  of  the  Sporangia  and  Gametophytes  of 
Selaginella  apus  and  Selaginella  rupestris,"  Bot.  Gaz.  32  :  124  and  170. 


A    PINE. 

Pinus  Austriaca,  or  P.  laricio. 

GYMNOSPERMS;  CONIFERALES;  PINACE^E. 

PRELIMINARY. 

IN  many  parts  of  the  country  the  only  living  pines 
are  those  that  have  been  planted  for  ornament.  Several 
species  have  been  introduced  in  this  way,  and  although 
in  some  localities  a  relatively  small  number  of  individuals 
are  found,  the  number  is  sufficient  to  make  the  collection 
of  materials  fairly  easy.  The  Austrian  pine  has  two 
polished  dark-green  needle-leaves  in  a  group.  The 
cones  in  which  the  seeds  form  are  ten  to  fifteen  centimeters 
long  and  are  relatively  smooth. 

The  Scotch  pine,  with  its  leaves  also  in  pairs,  may  be 
distinguished  from  the  Austrian  pine  by  its  shorter  leaves 
(eight  centimeters),  its  shorter  cones  (eight  centimeters) 
with  their  scales  having  prominent  projections  on  the 
free  ends,  which  toward  the  base  of  the  cone  are  curved; 
and  also  by  a  grayish  powdery  coating  upon  the  leaves. 

Early  during  the  growing  season,  usually  in  the  month 
of  May,  two  kinds  of  young  cones  may  be  distinguished. 
At  the  tip  of  the  young  shoots  very  small  megasporan- 
129 


13°  A  PINE. 

giate  or  carpettate  cones  may  be  seen  appearing  as  small 
side  branches.  At  the  base  of  young  shoots  the  clusters 
of  micros porangiate  or  staminate  cones  appear. 

They  do  not  usually  appear  on  the  same  young  shoot 
as  the  others,  and  a  tree  usually  bears  many  more  of 
one  kind  than  of  the  other.  The  staminate  cones  shed 
their  pollen  (microspores)  early  in  the  season. 

Specimens  of  both  kinds  of  cones  should  be  collected 
at  the  time  the  staminate  cones  are  about  ripe,  together 
with  the  young  shoots  and  needle-leaves.  At  the  same 
time  some  of  the  oldest  carpellate  cones  should  be  col- 
lected. In  the  winter  one-year-old  and  two-year-old  cones, 
and  the  buds  enclosing  growing  tips,  should  be  collected. 
All  collections  of  entire  specimens  should  be  preserved 
in  alcohol,  and  the  data  of  collecting  carefully  recorded. 
In  addition  to  these,  young  cones  of  both  kinds  and  also 
carpellate  cones  about  a  year  old  should  be  collected  and 
preserved  for  sectioning  of  the  sporangia  by  imbedding. 
Leaves  and  branches  may  be  gathered  at  almost  any  time, 
it  being  best  to  have  them  fresh  at  the  time  the  study 
is  made.  The  resinous  material  is  removed  by  putting  the 
specimens  in  alcohol,  for  at  least  a  day  or  two  before  using 
them. 

LABORATORY  WORK. 
GROSS  STRUCTURE. 
I.  GENERAL  CHARACTERS.     Observe: 

1.  The  central  axis  or  stem ;  its  few  main  branches,  and  numer- 
ous very  short  dwarf  branches,  each  bearing: 

2.  A  pair  of  slender  elongated  needle-leaves. 

3.  Scale-leaves  upon  the  stem,  about  the  dwarf  branches,  and 
base  of  needle-leaves,  and  covering  the  terminal  buds. 


PIN  US  AUSTRIACA,  OR   P.  LARICIO.  131 

4.  Near  the  bases  of  some  of  the  young  shoots: 

a.  The  clusters  of  staminate  cones  or  flowers,  each  com- 
posed of  crowded  stamens  (microsporophylls) ;   and  at 
the  tips  of  other  young  shoots: 

b.  The  very  small  carpellate  cones  or  flowers,  each  com- 
posed of  closely  crowded  carpels   (megasporophylls) ; 
and  on  older  parts  of  the  branch: 

c.  Larger,  heavy,  woody,  carpellate  cones. 

II.  THE  STEM. 

On  a  branch  eighteen  inches  or  two  feet  in  length  observe: 

1.  The  marks  indicating  the  beginning  and  ending  of  each 
year's  growth. 

2.  On  the  last  year's  growth,  the  scale-leaves. 

3.  Whether  scale-leaves  are  on  each  year's  growth. 

4.  The  relative  vigor  of  terminal  and  lateral  shoots. 

5.  The  buds  at  the  tips  of  shoots. 

6.  The  arrangement  of  the  dwarf  branches  that  bear  the 
needle-leaves. 

Cut  across  a  three-  or  four-year-old  shoot  and  observe: 

7.  The  central  pith  region. 

8.  The  outer  chlorophyll-bearing  bark  region. 

9.  Between   these   the  woody  region.     The  annual  growth 
rings  indicate  the  age  of  the  shoot.    Sketch  the  cross-sec- 
tion. 

III.  THE  LEAVES. 

i.  Scale-leaves.     Observe: 

a.  The  size,  form,  position,  and  arrangement  of  scale- 
leaves  on  main  shoots.     Note  the  differences  between 
scale-leaves   on  dwarf  shoots  enveloping  needle-leaves 
and  those  about  buds. 

b.  The  scars  left  as  scale-leaves  that  surround  the  bud 
are  dropped. 

c.  Draw  one  or  two  scale-leaves  of  each  kind. 


13*  A   PINE. 

2.  Needle-leaves.     Observe: 

a.  How  the  weak  bases  of  each  pair  of  leaves  are  enclosed 
and  stiffened  by  a  sheath  of  scale-leaves. 

b.  The  toughness  of  the  mature  needles.     Remove  a  pair, 
pull  away  the  scale-leaves,  and  observe: 

c.  The  dwarf  branch  on  which  the  needles  are  borne. 

d.  Draw  a  pair  of  leaves  upon  the  branch  that  bears  them. 
IV.  THE  CONES. 

1.  Staminate  cones.     Remove  from  the  cluster  one  cone,  note 
and  make  sketches  showing  the  outward  appearance,  the 
arrangement  of  the  sporophylls  that  compose  it,  and  a 
single  microsporophyll,  showing  top  and  edge  views. 

2.  Carpellate  cones. 

a.  Young    cone.     By   use  of   material    collected     about 
June  ist,  observe  the  young  cones  emerging  as  lateral 
branches  at  the  tip  of  the  young  growth  of  shoot  and 
needle-leaves.      The  separate  sporophylls  are  not  con- 
spicuous, but  may  be  distinguished  easily.     Sketch. 

b.  One-year-old  cone.     On  some  one-year-old  shoots  may 
be  seen  cones  that  have  grown  considerably  and  that 
have  changed  greatly  from  the  appearance  of  the  very 
young  cones. 

c.  Two-year-old  cones.     Observe: 

i.  The  outer  appearance  and  arrangement  of  mega- 

sporophylls  or  carpels.1 
ii.  The  completely  sealed  condition  of  old  cones  that 

were  collected  early  in  the  spring, 
iii.  Draw. 

Remove  some  of  the  sporophylls,  and  observe: 
iv.  The  general  form. 

v.  The  seeds,  and  seed-wings  borne  upon  them, 
vi.  Draw. 

1  For  full  statement  regarding  the  structure  of  the  carpel,  see  Coulter 
and  Chamberlain's  "Seed  Plants,"  Vol.  i  (Gymnospenms),  pp.  69-77. 


PINUS  AUSTR1ACA,  OR  P.  LARICIO.  133 

MINUTE  STRUCTURE. 
I.  THE  STEM. 

Make  a  transverse  section  of  a  year-old  stem,1  collected  in 
May  or  June,  and  study  the  different  tissues  composing  it  as 
follows: 

1.  The  pith,  occupying  the  center  of  the  section.     Observe: 

a.  The  general  outline  of  the  region.     In  some  sections 
will  be  seen  portions  of  the  pith  that  run  outward.   These 
lead  into  branches. 

b.  The  form  and  arrangement  of  the  cells. 

c.  The  contents  of  cells;  test  for  starch. 

2.  The  wood  (xylem),  the  heavy- walled  tissue  surrounding 
the  pith,  and  separated  somewhat  regularly  into  wedge- 
shaped  masses  by  the  medullary  rays. 

Select  a  good  wedge  and  observe: 

a.  The  resin-ducts,  one  or  two  of  which  appear  at  the 
inner  edge  of  the  wedge.    Immediately  around  the 
duct  is  a  circle  of  very  thin  cells,  the  secreting  layer.     In 
each  of  these  cells  is  the  granular  nucleus,  characteristic 
of  secreting  cells  in  general.     Surrounding  the  secreting 
layer  and  much  more  prominent  is  a  layer  of  thick- 
walled  cells,  forming  a  sheath. 

b.  Between  the  resin-ducts  and  the  pith  a  few  very  small 
rounded  cells  with  rather  thick  walls,  the  primary  xylem 
vessels. 

c.  The  main  bulk  of  wood  fibers,  the  tracheids.    In  the 
wood  observe: 

i.  The  form  and  arrangement  of  the  tracheids. 
ii.  Their  emptiness. 

3.  In  the  thinnest  part  of  the  specimens  search  for  sections 

1  Sections  may  be  made  of  stems  by  using  material  that  has  been  pre- 
served in  alcohol  for  at  least  a  few  days,  then  soaked  in  a  mixture  of 
alcohol  and  glycerin.  Such  sections  may  be  used  directly  or  may 
be  rendered  somewhat  more  satisfactory  by  use  of  differential  stains. 


134  A   PINE. 

of  the  bordered  pits,  characteristic  of  the  wood  of  the  group 
of  plants  to  which  the  pines  belong.1 

4.  Outside  the  xylem,  a  thin  layer  of  cambium  tissue,  seen 
only  in  sections  cut  with  extreme  care  from  stems  collected 
during  the  growing  season. 

5.  The  phloem,  the  whitish  tissues  outside  the  xylem  and 
cambium,  composed  of: 

a.  Angular,  whitish    cells   making   up    the  greater  part, 
the  sieve-cells.2 

Compare  the  shape  of  active  sieve-cells  next  the 
cambium  and  those  near  the  outside  of  the  phloem, 
which  have  become  functionless  with  age. 

b.  Near  the  periphery  of  the  sieve-tissue  an  interrupted 
row  of  cells  with  brown  or  yellow  contents  in  which 
are  strongly  refringent   crystals.     Near  the  cambium 
a  similar  row  of  cells,  larger  and  rounder  than  the  sieve- 
cells  and  with   colorless  or  slightly  yellowish  homo- 
geneous contents,  in  which  a  small  crystal  or  two  may 
sometimes  be  seen.    These  two  broken  rows  of  cells 
are  the  phloem  parenchyma.3 

6.  The  cortical  parenchyma,  lying  just  outside  the  phloem. 
Observe. 

a.  The  shape,  size,  and  arrangement  of  the  cells.     Com- 
pare with  the  pith  parenchyma  in  these  respects. 

b.  The  contents  of  cells,   including  the  distribution  of 
chlorophyll. 


1  For  a  clear  idea  regarding  the  structure  of  the  bordered  pits,  as 
well  as  for  a  knowledge  of  the  structure  and  relations  of  the  other  parts 
of  the  wood  of  the  pine,  see  Strasburger's  "Botanisches  Practicum," 
Coulter  and  Chamberlain's  "Gymnosperms,"  and  other  text-books. 

2  So  called  because  the  radial  walls  of  these  cells  are  perforated  by 
clusters  of  very  fine  pits,  the  sieve-plates;  they  occupy  the  same  relative 
position  as  the  bordered  pits  of  the  tracheids. 

3  These  two  tissues  of  the  phloem  can  be  well  demonstrated  by  means 
of  differential  stains. 


PINUS  AUSTRIACA,  OR  P.  LARICIO.  135 

c.  The  resin-ducts.  Compare  their  structure  with  that 
of  the  ducts  in  the  xylem. 

7.  By  use  of  a  very  thin  section  study  the  medullary  rays, 

observing : 

a.  The  rays  extending  from  the  pith  to  the  cortical  paren- 
chyma. 

6.  The  shape  of  the  cells  in  the  xylem  and  the  gradual 
transition  into  the  cortical  parenchyma. 

c.  The  cell  contents. 

8.  The  outermost  part  of  the  stem  is  composed  of  the  bases 

of  the  scale-leaves.     In  one  leaf-base  observe: 

a.  An  inner  layer  of  very  thin-walled  irregular  cells. 

b.  An  outer  layer  of  one  or  two  rows  of  large  cells  upon 
which  is  a  single  row  of  epidermal  cells.     Observe: 

i.  The  thickening  of  the  outer  epidermal  wall,  and 
ii.  The  continuous  outer  layer  of  this  wall,   the  cu- 
ticle. 

9.  Make  a  diagram  of  the  entire  cross  section  and  label  the 
various  regions. 

10.  Draw  in  detail  a  narrow  strip  including  all  kinds  of  stem 
tissues  from  pith  to  epidermis. 

11.  Make  a  thin  longitudinal  radial  section  of  a  year-old  stem, 
and  identify  by  their  arrangement  the  various  kinds  of 
tissues  seen  in  the  transverse  section,  and  study  the  differ- 
ence in  shape  of  cells  in  this  section. 

12.  Draw  in  detail  small  regions  which  show  structures  not 
seen  in  cross-section. 

Make  a  thin  tangential  section  through  the  wood.     Observe 
especially: 

13.  Ends  of  medullary  rays. 

a.  The  number  of  rows  of  cells  in  thickness  and  height  of 
each  ray. 

b.  The  thin  parts  of  the  walls  corresponding  to  the  pits. 

c.  Draw,  including  a  few  adjacent  tracheids. 


136  A   PINE. 

14.  Sections  running  in  various  directions  through  bordered 
pits. 

15.  The  very  tapering  ends  of  tracheids. 
II.  THE  LEAF. 

Make  a  cross-section  of  the  needle-leaf,  mount  and  note  the 
following  regions: 

1.  The   outer   heavy-walled   epidermal   and    strengthening 
region. 

2.  The  mesophyll  region,  made  conspicuous  by  the  presence 
of  chlorophyll. 

3.  The  vascular  bundle  region,  composed  of  light-colored  cells 
and  surrounded  by  a  distinct  row  of  cells,  the  bundle- 
sheath. 

4.  Make  a  diagram  showing  the  form  of  the  cross-section,  and 
the  relative  position  and  extent  of  each  region. 

Study  the  details  of  each  region  as  follows: 

5.  Epidermis. 

a.  The  thick  cuticle. 

b.  The  epidermal  cells,  their  very  thick  walls  and  the 
peculiar  thickening  within  the  cells. 

c.  At  somewhat  regular  intervals  the  stomata,  each  stoma 
consisting  of: 

i.  An  outer  chamber  which  appears  as  a  depression 

in  the  cuticle  and  epidermal  layer. 
ii.  An  inner  chamber  lying  within  the  chlorophyllose 

tissue  immediately  below  the  outer  chamber, 
iii.  A  narrow  opening  connecting  the  two  chambers, 
iv.  At  the  sides  of  the  outer  chamber  are  two  promi- 
nent  epidermal   cells,    and   immediately   beneath 
these  are: 

v.  Two  smaller  guard-cells    distinguishable   by  con- 
taining chlorophyll. 

6.  The  incomplete  layer  of  cells  immediately  below  the  epi- 
dermis, the  sderenchyma  or  hypoderma.     Observe: 


PIN  US  AUSTRIACA,  OR  P.  LARICIO.  137 

o.  The  number  of  rows  of  cells  in  thickness  in  different 
parts  of  the  section,  and  their  compactness. 

b.  The  especial  adaptation  for  strengthening  the  leaf  at 
its  angles. 

c.  The  small  circular  (in  section)  cell  cavity,  and  the 
heavy  walls  with  pore-pits. 

7.  The  mesophyll. 

a.  The  shape  of  the  cells,  the  average  number  of  rows 
between  the  hypoderma  and  the  bundle-sheath. 

b.  The  infoldings  of  the  wall,  dividing  the  cavity  into 
recesses.     Observe  the  position  of  the  most  prominent 
of  these  infoldings  in  the  outermost  row  of  mesophyll- 
cells.     Observe  occasionally  (usually  near  a  stomatal 
cavity)  branched  cells. 

c.  In  fresh  specimens  the  abundant  chlorophyll. 

d.  The   resin-ducts;    compare   their  structure  with  that 
of  the  ducts  in  the  stem.     Notice  the  thick  walls  of 
the  sheath-cells. 

8.  The  vascular  bundle  region. 

a.  The  bundle-sheath;  shape  and  contents  of  the  cells. 

b.  The  two  masses  of  small  cells,  the  two  vascular  bundles. 
Each  bundle  is  distinctly  divided  into  a  xylem  and 
phloem  area.     A  partially  developed  resin-duct  some- 
times appears  in  the  xylem. 

c.  Surrounding  the  bundles,   the  parenchyma,   some  of 
which   may   form   radial   rows   running   through   the 
bundles  as  medullary  rays. 

d.  Make  a  diagram  of  the  section  and  draw  a  narrow  strip 
across  it,  showing  in  detail  each  kind  of  tissue. 

III.  THE  MICROSPOROPHYLL. 

From  a  cone  that  was  collected  just  before  the  pollen-grains 
were  shed,  remove  some  of  the  stamens  and  observe: 
i.  Their  general  form. 


I3&  A  PINE. 

2.  The  parts  composing  each  stamen,  the  short  stalk  (the 
filament),  the  two  long  sporangia  that  make  up  almost  the 
entire  body,  and  the  flat  extension  at  the  outer  part.    Tear 
open  a  few  sporangia,  and  study  the  microspores  (pollen- 
grains),  observing: 

3.  The  central  cell  from  the  wall  of  which  two  lateral  blad- 
dery outgrowths,  the  "wings,"  have  developed. 

4.  Within  the  central  cell  the  granular  cytoplasm  and  usually 
one  or  two  nuclei.* 

5.  Draw  a  microspore. 

6.  Observe  the  structure  of  a  small  piece  of  the  sporan- 
gium wall  and  make  a  sketch  showing  it. 

IV.   THE  MEGASPOROPHYLL.2 

From  a  one-year-old  cone  remove  some  of  the  sporophylls 
and  observe: 

1.  On  each  sporophyll  one  or  two  elevations  on  its  upper 
side  near  the  axil,  between  it  and  the  axis  of  the  cone. 
These  are  the  megasporangia,  or  ovules. 

2.  The  open  end  of  the  ovule  extending  downward. 

3.  By  means  of  prepared  longitudinal  sections  of  the  ovule 
cut  perpendicular  to  the  flat  surface  of  the  carpel,  study 
the  structure  of  the  ovule,  observing  the  following  parts: 
a.  The  outer  covering  (the  integument)  extending  down- 
ward about  the  opening. 

1  If  there  are  two  nuclei,  it  is  evident  that  the  microspore  has  begun 
to  germinate  to  produce  the  male  gametophyte  and  male  cells.     Often 
one  of  the  new  cells  formed  through  division  of  the  spore  nucleus  will 
be  seen  to  be  a  lenticular  one   rather  closely  pressed  against  one  side 
of  the  microspore  wall.     The  nucleus  of  the  other  cell  may  lie  anywhere 
in  the  larger  mass  of  cytoplasm. 

2  The  material  most  needed  will  be  found  in  cones  collected  at  the 
time  they  are  about  a  year  old.     If  there  is  at  hand  a  good  supply  of 
entire  cones  and  separate  sporophylls  collected  at  intervals  of  ten  days 
or  two  weeks  during  spring,  so  that  they  are  suitable  for  sectioning 
to  show  different  stages  of  development,   microtome  sections  should 
be  prepared.     See  Chamberlain's  "Methods  in  Plant  Histology,"  pp. 
119-121. 


PINUS  AUSTRIACA,  OR   P.  LARICIO.  139 

6.  The  opening,  the  micropyle. 

c.  The  tissue  enclosed  by  the  integument,  the  nucellus. 

d.  Within  the  nucellus  the  large  rounded  cell,  the  mega- 
spore,  or  the  embryo-sac  containing  female  gametophyte.1 

In  fully  developed  female  gametophytes  observe: 

e.  Their  general  form  at  their  micropylar  ends. 

/.  The  archegonia.     Study  the  archegonia  in  detail,  ob- 
serving: 
i.  The  large  base — the  egg — and  the  prominent  nucleus 

it  contains, 
ii.  The  neck  opening  toward  the  micropyle. 

g.  In  some  cases  may  be  seen  pollen-grains  that  have  been 
deposited  on  the  nucellus,  and  from  which  pollen-tubes 
have  grown  toward  the  necks  of  the  archegonia  for  the 
purpose  of  carrying  the  male  cells  to  the  egg.2  Ob- 
serve especially  the  tortuous  course  of  the  pollen-tube. 

h.  In  older  ovules  the  young  embryo  of  the  sporophyle 
may  be  seen.  Note  its  form  and  structure;  also  how 
it  has  used  up  adjacent  gametophyte  tissue  as  food. 

i.  From  fully  developed  ovules  (seeds')  dissect  out  the 
embryo  and  note  root,  stem,  and  cotyledons  (seed-leaves), 
noting  also  how  completely  it  is  surrounded  by  the 
female  gametophyte  tissue.  Identify  in  the  seed  the 
various  parts  of  the  ovule. 

/.  Observe  the  wing  on  fully  ripened  seeds.  Drop  one  from 
a  height  of  a  few  feet,  and  time  its  fall.  Then  tear  away 

1  In  most  cases  the  student  will  find  no  megaspore  within  the  sporan- 
gium, since  the  megaspore  will  have  germinated  to  produce  the  embryo- 
sac   and   female   gametophyte.     These  are   enclosed   by   the   nucellar 
tissue.     In  prepared  sections  they  are  often  so  contracted  as  to  be 
pulled  away  from  the  surrounding  nucellar  tissue. 

2  Since  the  male  gametophyte  and  male  cells  are  at  first  entirely  enclosed 
by  the  wall  of  the  former  microspore,  in  order  to  bring  the  male  cells 
into  the  vicinity  of  the  female  gamete  (egg),  the  entire  microspore  with 
its  contents  is  carried  by  the  wind  to  the  nucellus  of  the  sporangium. 
This  transfer  of  microspores  is  called  pollination.     When  the  spore  is 
located  on  the  nucellus  the  processes  of  fertilization  may  begin. 


140  A    PINE. 

the  wing  and  time  the  fall  of  the  seed  alone.     What 
would  be  the  effect  in  a  wind? 

k.  Make  a  drawing  illustrating  the  carpel,  and  the  ovule 
with  its  various  parts  as  outlined  above. 

ANNOTATIONS. 

The  pine  raises  a  strong  tall  stem  above  the  ground, 
thus  better  exposing  its  leaves  to  the  light.  This  stem 
also  serves  better  to  expose  the  flowers  so  that  pollination 
may  be  effected  and  that  ripened  seeds  may  be  distributed. 
This  stem  habit  is  made  possible  through  the  extensive 
development  of  mechanical  and  supporting  tissues. 

The  stem  by  means  of  its  terminal  buds  may  continue 
its  growth  in  length,  and  also  may  continue  its  growth  in 
diameter  by  means  of  the  growth  cylinder — the  cambium 
layer — that  lies  between  the  xylem  and  phloem.  The 
difference  in  the  size  and  form  of  the  cells  added  to  the 
xylem  at  different  times  in  the  growing  season  gives  rise 
to  markings  or  annual  growth  rings  that  indicate  the 
age  of  the  stem. 

In  the  details  of  its  structure  the  stem  is  somewhat 
complex.  In  its  central  part  is  a  pith  region  composed 
of  ordinary  parenchyma  cells.  In  the  innermost  region 
of  the  xylem  are  a  few  greatly  elongated,  tubular  cells, 
trachea,  which  are  not  found  in  the  secondary  wood  of 
pines,  but  are  of  especial  interest  since  they  appear 
abundantly  in  the  wood  of  the  next  and  highest  group,  the 
Angiosperms.  In  the  Gymnosperms  the  bulk  of  the  wood 
is  almost  exclusively  made  up  of  tracheids.  In  the  de- 
velopment of  the  vascular  tissue  the  cells  become  greatly 
elongated,  and  in  tracheae  most  of  the  end  walls  of  the  cells 


PINUS  AUSTRIACA,  OR  P.  LARICIO.  141 

disappear,  leaving  the  vessels  as  continuous  tubes.  In 
tracheids  the  end  walls  do  not  disappear.  As  the  tra- 
cheids  in  the  pines  and  their  kin  develop,  the  lateral 
walls,  originally  thin  and  plain,  thicken  irregularly,  a 
part  of  the  thickening  on  each  side  of  the  primary  wall 
growing  away  from  it  to  form  the  "border"  of  the  small 
spot  that  remains  thin,  the  whole  constituting  the  "bor- 
dered pit."  Usually  the  primary  wall  remains  as  a 
membrane  separating  the  two  cells.  Should  it  be  de- 
stroyed, there  would  be  free  communication  between  the 
contiguous  cells. 

Outside  the  xylem  region  is  the  cambium  tissue,  com- 
posed of  a  few  layers  of  thin-walled  active  cells  from 
which  during  the  growing  season  new  cells  are  constantly 
formed  by  division.  In  the  phloem  just  outside  the 
cambium  the  leading  tissue-element  is  the  sieve-cells. 
These  are  elongated  cells,  the  side  and  end  walls  of  which 
have  become  perforated,  thereby  forming  "  si  eve-  plates," 
through  which  food  may  pass.  The  "sieve-cells"  are 
used  largely  as  transporting  and  temporary  storage 
regions  for  foods.  Outside  the  phloem  region  the  layers 
of  living  and  dead  cortex  are  formed. 

The  scale-leaves  are  entirely  protective,  while  the 
foliage  work  is  almost  exclusively  done  by  the  needle- 
leaves.  The  epidermis  and  sclerenchyma  of  the  needle- 
leaves  are  especially  thick- walled  and  serve  to  give  rigidity 
to  the  leaves,  and  to  protect  the  chlorophyll-bearing 
tissues  against  rapid  changes  in  temperature  and  too 
great  loss  of  water.  The  sunken  position  of  the  guard- 
cells  secures  them  against  stoppage  which  would  hinder 
the  entrance  of  necessary  gases. 


1+2  A   PINE. 

The  needle-leaves  are  borne  upon  dwarf  branches 
that  may  be  seen  when  the  sheathing  scale-leaves  are  re- 
moved. It  is  to  be  noticed  that  the  vascular  bundles  of 
all  the  needle-leaves  of  a  pair  or  group  borne  on  the  same 
dwarf  branch  have  their  xylem  portions  facing  a  common 
center,  while  their  phloem  portions  are  peripheral,  as 
would  be  true  in  an  ordinary  branch  from  the  stem.  The 
imbedding  of  the  vascular  bundles  in  a  group  of  colorless 
tissue  surrounded  by  a  sheath  is  common  among  the 
pines  and  their  allies.  Poorly  developed  resin-ducts 
are  occasionally  found  in  the  xylem  of  leaf-bundles,  al- 
though it  has  been  denied  by  some  writers. 

In  comparing  the  reproduction  of  the  pines  with  that 
of  the  plants  already  studied  we  find  advances  of  much 
interest.  In  the  Bryophytes  and  in  the  lower  Pterido- 
phytes  the  asexual  spores  upon  germination  develop 
relatively  prominent  structures  upon  which  sex-organs 
eventually  develop.  These  sex-organs  produce  gametes 
and  sexual  spores  from  which  grow  sporophytes,  upon 
which  the  asexual  spores  are  produced  in  their  turn. 
In  the  highest  Pteridophytes  the  asexual  spores  are 
unlike  in  size,  produce  unlike  gametophytes,  and  after 
germination  retain  the  gametophytes  within  their  walls. 
Fertilization  occurs  even  while  the  female  gametophyte 
is  within  the  old  cracked  megaspore  wall.  In  Selaginella 
the  embryo  sporophyte  not  only  begins  its  development 
within  the  female  gametophyte  while  this  is  enveloped 
by  the  ruptured  spore-wall,  but  often  while  the  megaspore 
still  lies  unshed,  enclosed  in  the  sporangium  which  pro- 
duced it.  Furthermore,  in  these  highest  Pteridophytes 
the  sporophylls  are  collected  into  distinct  cones. 


PINUS  AUSTRIACA,  OR  P.  LARICIO.  143 

In  the  pines  the  sporophylls  are  likewise  gathered  into 
cones,  but  the  two  kinds  of  cones  are  unlike,  due  to 
the  difference  in  the  sporophylls  that  compose  them. 
The  megasporangia  (ovules)  are  produced  upon  the 
megasporophylls  (carpels)  and  the  microsporangia  (pollen- 
sacs)  upon  microsporophylls  (stamens).  The  mega- 
sporangium  does  not  open  and  therefore  the  megaspore 
is  never  shed,  but  germinates,  as  often  in  Selaginella, 
within  the  tissues  of  the  sporangium  (ovule).  There  it 
produces  a  female  gametophyte  which  remains  enclosed 
within  it,  because  it  does  not  grow  large  enough  to  rupture 
the  spore-wall,  yet  the  gametophyte  bears  distinct  arche- 
gonia.  Since  these  archegonia  are  not  exposed,  the 
male  gametes  cannot  gain  entrance  to  them  by  swimming 
in  water  as  heretofore,  even  were  such  a  medium  present. 

The  microspore  (pollen-grain)  may  begin  its  germina- 
tion before  it  leaves  the  sporangium  or  afterward.  Since 
these  pollen-grains  are  carried  in  quantity  by  the  wind, 
one  or  more  of  them  may  be  deposited  on  the  nucellus 
of  the  ovule.  From  the  inner  wall  of  those  favorably 
deposited  there  develops  a  tube  that  grows  parasitically 
through  the  sporangium  and  spore- wall  to  an  archegonium 
on  the  female  gametophyte.  The  male  cells,  which  may 
have  been  formed  before  or  after  the  tube  began  to  grow, 
migrate  to  the  end  of  the  tube  which  passes  to  the  neck 
of  the  archegonium.  At  this  time  the  end  of  the  tube 
opens  and  allows  the  male  cells  to  escape.  One  male 
cell  unites  with  the  egg,  thus  producing  the  oospore.1 

1  It  is  noteworthy  that  in  several  other  Gymnosperms  ciliated  sperms 
have  been  found.  Such  structures  suggest  the  existence  formerly  of  a 
watery  medium  enabling  them  to  pass  by  swimming  from  the  male 
gametophyte  to  the  egg. 


144  A   PINE. 

It  is  important  to  observe  also  the  long  time  required  to 
effect  the  development  of  the  pollen-tube  and  the  sub- 
sequent fertilization,  for  about  a  year  elapses  between 
the  transfer  of  the  microspore  to  the  megasporangium 
before  fertilization  actually  occurs.  More  highly  spe- 
cialized plants,  as  some  Angiosperms,  grow  pollen-tubes 
many  times  as  long  as  those  of  the  pine  in  an  almost 
incredibly  short  time,  often  in  the  course  of  a  few  hours. 

The  oospore  germinates  and  produces  the  embryo 
sporophyte.  As  this  goes  on,  the  whole  sporangium 
grows,  and  by  the  time  the  rudimentary  root,  stem,  and 
leaves  are  formed  the  outer  parts  of  the  ovule  have  become 
dry  and  hard,  forming  the  testa,  and  the  embryo  itself 
has  entered  upon  a  dormant  period.  In  this  state  the 
whole  structure  constitutes  a  seed.1 

As  the  ovule  grows  and  ripens  the  upper  surface  of 
the  carpel  becomes  separated  from  the  main  body,  and 
remains  attached  to  the  seed  as  the  wing. 

In  the  spring  or  early  summer  succeeding  the  ripening 
of  the  seed,  by  the  drying  and  warping  of  the  carpels, 
the  cones  open  and  the  seeds  are  shaken  out  by  winds 
which,  because  of  the  buoyancy  of  the  wings,  carry  away 
the  seeds  to  some  distance  from  the  parent  tree.  Under 
favorable  conditions  the  embryo  resumes  its  growth, 
emerges  from  the  seed-coat,  and  begins  to  establish  itself 
as  a  new  (pine-plant)  individual. 

1  It  will  be  interesting  in  this  connection  to  review  from  Coleochcele 
to  Pinus  the  effect  produced  upon  adjacent  tissues  by  the  act  of  fer- 
tilization. See  also  "The  Origin  of  Gymnosperms  and  the  Seed  Habit," 
by  John  M.  Coulter,  Bot.  Gaz.  26  :  153-168,  and  "Origin  of  {he.  Leafy 
Sporophyte,"  by  John  M.  Coulter,  Bot,  Qaz.  28  :  46-59. 


WAKE-ROBIN. 

Trillium  sp. 

ANGIOSPERMSJ     MONOCOTYLEDONS;        LILIACE^. 

PRELIMINARY. 

THE  various  species  of  Trillium  may  be  found  flowering 
in  rich  woods  in  early  spring.  The  plants  are  easily 
distinguished  from  others  by  the  straight  naked  stems 
that  are  fifteen  to  thirty  centimeters  in  height,  the  circle 
of  three  broad  net-veined  leaves,  and  the  single  terminal 
flower  with  three  floral  organs  in  each  cycle.  The  flow- 
ers vary  considerably  in  the  different  species,  but  any  of 
these  species  will  serve  well  for  this  study.1 

If  the  laboratory  study  is  not  to  be  made  at  the  time 
Trilliums  are  flowering,  a  good  supply  should  be  preserved 
both  dry  and  in  alcohol  or  formalin  for  class  work. 

1  In  case  material  for  work  with  Trillium  cannot  be  had,  in  place 
of  it  may  be  used  the  hyacinth,  tulip,  lily  (Lilium),  wild  onion  (Allium), 
or  any  other  such  plant  belonging  to  the  Monocotyledons,  the  group 
to  which  Trillium  belongs.  In  case  one  of  these  is  used,  the  outline 
given  for  Trillium  will  serve  to  guide  the  study  in  a  general  way. 

MS 


146  WAKE-ROBIN. 

LABORATORY    WORK. 
GROSS  STRUCTURE. 

I.  GENERAL  CHARACTERS.    Observe: 

1.  The  main  axis  consisting  of  a  thickened,  horizontal  under- 
ground stem,  the  rhizome  or  root-stalk,  and  a  single  verti- 
cal branch,  the  aerial  stem,  bearing  a  terminal  flower. 

2.  The  root-stalk,  bearing   as  lateral  appendages  the  roots 
and  modified  leaves  in  the  form  of  broad  membranous 
scales. 

3.  The  aerial  stem,  bearing  as  lateral  appendages  a  whorl  of 
three  foliage  leaves,  and  the  parts  of  the  flower,  in  five 
whorls. 

II.  THE  ROOTS.     Observe: 

1.  Their  arrangement  on  the  root-stalk. 

2.  The  absence  of  branching. 

3.  The  surface,  especially  the  transverse  wrinkles  on  older 
parts.     What  is  the  significance  of    the  wrinkles  ? 

If  quite  fresh  specimens  are  used,  it  may  be  possible  to  see: 

4.  The  root-hairs. 

III.  THE  ROOT-STALK  (RHIZOME).    Observe: 

1.  Its  shape  and  thickness. 

2.  The  succession  of  nodes  and  internodes. 

a.  Their  number  in  an  unbroken  root-stalk. 

b.  The  scars  of  former  branches,  and  the  varying  number 
of  intervening  nodes. 

c.  The  irregular  growth  of  the  internodes. 

3.  The  apical  bud  and  its  protecting  scales. 

4.  Sketch  a  piece  of  the  root-stalk  with  some  of  the  roots 
growing  upon  it. 

IV.  THE  BRANCH  (aerial  stem). 

1.  The  absence  of  nodes  below  the  whorl  of  leaves. 

2.  The  smoothness  of  the  surface. 


TRILLIUM  SP.  147 

V.  THE  LEAVES. 

1.  The  scale-leaves  of  the  root-stalk. 

a.  The  bases  of  decayed  scales  at  each  node. 

b.  Younger  ones  sheathing  the  apex  of  the    root-stalk, 
the  bud,  and  base  of  the  aerial  branch. 

2.  The  foliage  leaves. 

a.  Their  number,  arrangement,  and  shape. 

b.  The  outline  of  the  base,  margin,  and  apex. 

c.  The  leaf-stalk  or  petiole  (not  present  in  all  species). 

d.  The  system  of  veining. 

3.  Draw  different  forms  of  scales  and  one  foliage  leaf. 

VI.  THE  FLOWER.     Observe: 
i.  The  parts  of  the  flower. 

a.  The  lower  cycle  of  green  leaves,  the  calyx,  each  mem- 
ber of  which  is  a  sepal. 

b.  The  cycle  of  colored  leaves  above  the  calyx,  the  corolla, 
each  member  of  which  is  a  petal. 

c.  The  two  cycles  of  organs  next  above  the  corolla,  each 
member  of  which  is  a  microsporophyll  or  stamen.    In 
one  stamen  observe: 

i.  The  stalked  base,  the  filament. 

ii.  The  enlarged  tip,  the  anther,  showing  on  its  inner 
face  four  swellings,  the  microsporangia.  In  an- 
thers that  have  opened,  masses  of  microspores 
(pollen-grains)  may  usually  be  seen. 

d.  The  innermost  organ  of  the  flower,  made  up  of  three 
megasporophylls    or    carpels   united  into    one    pistil. 
Each  pistil  is  composed  of: 

i.  An  enlarged  base,  the  ovary,  in  which  megasporan- 
gia  or  ovules  are  formed.  Tear  open  the  ovary  and 
locate  the  ovules. 

ii.  A  short  tapering  portion  immediately  above  the 
ovary,  the  style. 


14$  WAKE-ROBIN. 

iii.  A  roughened  or  hairy  surface  on  the  inner  and 
upper  part  of  each  style,  the  stigma.  Note  whether 
any  microspores  (pollen-grains)  are  attached  to  the 
stigma. 

2.  That  the  parts  of  the  flower  arise  from  the  end  of  a  stem 
which  is  broadened  to  form  the  receptacle. 

3.  That  all  other  parts  are  placed  below  the  pistil,  that  is,  they 
are  hypogynous. 

4.  That  each  cycle  is  made  up  of  a  definite  number  of  organs. 

5.  That  the  members  of  one  cycle  of  floral  organs  alternate 
in  position  with  the  members  of  the  succeeding  cycle. 

6.  Sketch  an  entire  flower,  then  one  member  from  each  set 
of  organs  that  compose  it. 

MINUTE  STRUCTURE. 
I.  THE  ROOT. 

In  a  central  longitudinal  section  through  a  root-tip  observe 
the  following  regions:  * 

1.  The  outer  looser  cells  and  the  inner  more  compact  tissues 
forming  the  root-cap.     This  is  disconnected  from  the  root 
except  at  the  foremost  portion. 

2.  In  the  center  of  the  section  and  immediately  under  the  end 
of  the  root-cap,  a  group  of  small  angular  cells,  the  primary 
meristem,  corresponding  to  the  apical  cell  in  the  fern-root. 
These  constitute  the  region  of  most  active  cell-formation. 

3.  Originating    in  the  primary  meristem    are  regions  that 
finally  form  the  permanent  tissues  of  the  root.     They  are: 
a.  The  dermatogen,  an  outer  layer  of  cells  on  the  root  proper, 

beneath  the  root-cap.  This  layer  later  becomes  the 
epidermis,  though  it  is  not  easy  to  distinguish  it  as  such, 
since  it  is  probably  a  transient  structure  in  the  root. 

1  As  it  is  difficult  to  secure  uninjured  tips  of  Trillium,  an  onion  partly 
submerged  in  water  for  a  few  days  will  supply  substitutes  that  are  even 
better. 


TRILLIUM  SP.  149 

b.  The  central  cylindrical  mass  of  cells,  the  plerome,  that 
finally  becomes  the  fibrovascidar  bundle  region  or  the 
stele. 

c.  Between  the  dermatogen  and  plerome  is  the  periblem, 
from  which  the  cortex  is  finally  developed. 

If  the  material  is  favorable,  observe: 

4.  The  root-hairs.     Observe  on  what  part  of  the  root  they 
are  borne,  also  their  relation  to  the  epidermal  cells. 

5.  Diagram  the  regions  observed. 

6.  Make  a  transverse  section  of  the  root  a  litttle  way  back 
from  the  tip,  and  identify  the  permanent  regions  mentioned 
in  the  study  of  the  longitudinal  section. 

7.  Diagram  the  transverse  section. 

II.  THE  APICAL  BUD  OF  THE  RHIZOME. 

Divide  the  tip  longitudinally  and  on  the  cut  surface  observe: 

1.  The  shape. 

2.  The  sheathing  membranous  scales. 

3.  Beneath  the  scales  the  small  growing  point  of  the  stem. 
On  this  may  sometimes  be  seen  rudimentary  scales. 

4.  In  some  such  sections  one  may  also  see  the  base  of  rudi- 
mentary branches. 

5.  Diagram  the  section. 

III.  THE  AERIAL  STEM.* 

Make  a  transverse  section  and  observe: 

1.  The  single  row  of  epidermal  cells.     Note  the  form  of  the 
cells  and  the  thickness  of  their  walls. 

2.  The  large  loosely  arranged  tissue  with  intercellular  spaces, 
the  parenchyma. 

a.  The  shape  of  the  cells. 

b.  Relative  thickness  of  the  walls. 

c.  Intercellular  spaces. 

1  It  may  be  found  advisable  to  use  instead  of  the  section  of  a  Trillium 
stem  that  of  corn  (Zea  mats)  or  some  other  Monocotyledon. 


15°  WAKE-ROBIN. 

3.  The  vascular  bundle  region. 

a.  The   irregular    bundle-sheath   surrounding   the   entire 
region. 

b.  Groups  of  conducting  tissue  distributed  through  the 
region,  the  vascular  bundles.     Note  their  distribution 
and  approximate  number.     Each  so-called  bundle  is 
really  a  pair  of  strands,  being  composed  of  two  inde- 
pendent parts  as  follows: 

(1)  The  phloem  strand,  the  outer  part  of  the  bundle, 
consisting  of  angular,  thin-walled  cells  of  various 
sizes.     The  larger  cells  are  the  sieve-cells  through 
which  most  of  the  manufactured  foods  are  thought 
to  be  transported. 

(2)  The  xylem  strand,  consisting  of  very  thick-walled 
cells  of  various  sizes.     In  a  young  stem  this  tissue  is 
less  abundant  than  the  phloem,  while  in  old  stems 
it  is  more  abundant.     It  is  closely  associated  with 
the  fibrous  tissue  that  more  or  less  invests  the  bun- 
dle.    In  very  young  bundles  between  the  phloem 
and  the  xylem  is  a  growing  or  meristem  tissue  known 

as  the  cambium.1 

4.  Draw  a  portion  of  the  entire  cross-section  in  which  the 
structural  elements  mentioned  above  are  shown. 

IV.  THE  LEAF. 

Carefully  peel  off  and  mount  epidermis  from  both  surfaces 
of  the  leaf  and  observe: 

1.  The  form  of  epidermal  cells. 

2.  The  stomata.     Each  stoma  consists  of: 
a.  Two  crescentic  guard-cells,  and 

1  In  Monocotyledons  all  of  this  tissue,  ceasing  to  divide  sooner  or 
later,  becomes  changed  into  xylem  or  phloem,  thus  producing  a  so-called 
"  closed  "  bundle,  while  in  Dicotyledons  the  persistent  cambium  makes 
possible  a  constant  increase  in  diameter,  the  bundle  being  therefore 
'  open." 


TRILLIUM  SP.  I$I 

b.  The  stomatal  slit,  that  extends  between  the  guard- 
cells  and  below  the  epidermis  expands  into  the  stomatal 
cavity.  Observe  whether  stomata  appear  on  both  leaf 
surfaces. 

3.  Draw   small   regions   from   epidermis   of  both   surfaces. 
Make  a  very  thin  transverse  section  of  the  leaf,1  and 
observe: 

4.  The  epidermal  cells  on  both  edges.     Compare  with  the 
surface  view. 

5.  Stomata.     Find  in  the  thinnest  part  of  the  preparation 
a  section  truly  transverse  to  the  guard-cells  and  compare 
with  surface  view.     Observe  the  stomatal  cavity  between 
and  below  the  guard-cells,  and  note  its  relation  to  : 

6.  The  mesophyll  tissue.     In  this  region  observe: 

a.  The  palisade  mesophyll  of  compact  columnar  cells  with 
ends  outward. 

b.  The  spongy  or  loosely  arranged  mesophyll  below  the 
palisade  tissue. 

7.  Cross-section  of  veins  of  the  leaf  enclosed  by  the  mesophyll. 
Identify,  from  comparison  with  the  stem,  the  tissues  in  the 
vein. 

8.  Draw  a  part  of  the  section. 
V.  REPRODUCTION. 

i.  The  stamen,  microsporangia,  and  microspores  (pollen). 
In  a  cross-section  of  a  young  anther  observe: 
a.  The  four  sporangia  in  which  are  spores  in  process  of 

development.2 
In  a  cross-section  of  a  ripe  anther  observe: 


1  This  will  be  far  more  satisfactory  if  made  with  a  microtome. 

1  By  means  of  material  ranging  in  age  from  that  of  very  young  flower- 
buds  to  buds  nearly  ready  to  open,  it  is  possible  to  make  out  an  interest- 
ing and  instructive  series  in  the  process  of  spore  development.  Still 
younger  buds  will  show  interesting  stages  in  the  development  of  the 
sporophylls. 


152  WAKE-ROBIN. 

b.  That  the  four  sporangia  are  ready  to  open  in  pairs, 
thus  forming  two  pollen-sacs. 

c.  The  thinness  of  the  sporangium  wall,  and  the  place 
especially  formed  for  opening  the  anther.     The  act  of 
opening  the  sporangia  is  known  as  dehiscence. 

d.  The  microspores  (pollen-grains). 

e.  Diagram  the  section. 

2.  The  formation  of  male  gametes.     In  many  cases  the  micro- 
spores  will  have  germinated  before  they  have  left  the  an- 
ther.   In  germination  the  spore  nucleus  divides,  thus  form- 
ing a  so-called  generative  nucleus  and  a  tube  nucleus.     The 
latter  is  associated  with  the  development  of  a  pollen-tube. 
The  generative  nucleus  finally  divides,  thus  forming  two 
male  gametes.     It  is  the  rule  for  this  last  division  not  to 
occur  until  after  the  pollen-grain  has  left  the  anther.     The 
results  of  the  first  division  may  often  be  observed  within 
the  walls  of  microspores  still  in  the  anther. 

3.  The   carpels,   megasporangia   (ovules),   and   megaspores. 
By  means  of  cross-section  of  the  ovary1  observe: 

a.  Ovules  that  appear  as  somewhat  oval  bodies  attached 
by  their  bases  to  the  central  axis  of  the  ovary.     In 
Trillium  the  ovules  are  curved,  having  their  tips  turned 
toward  their  bases  and  also  toward  the  central  axis  of 
the  ovary.     Selecting  one  good  ovule,  observe: 
i.  The  outer  covering  of  the  ovule,  the  integuments. 
ii.  The  opening  between  the  ends  of  the  integuments, 

the  micropyle. 
iii.  The  tissue  of  the  ovule  beneath  the  integuments, 

the  nucellus. 
iv.  Within  the  nucellus  the  single  large  megaspore,  or 

the  embryo-sac  that  has  developed  from  it. 
v.  Diagram  the  section. 

1  A  good  set  of  permanent  serial  sections  of  the  ovules  illustrating 
developmental  stages  should  be  at  hand. 


TRILLIUM  SP.  153 

4.  The  embryo-sac  and  female  gametophyte.  From  the 
megaspore  that  is  formed  within  the  nucellus  of  the  ovule 
(megasporangium)  the  embryo-sac  with  the  contained 
female  gametophyte  develops.  When  the  spore  first 
begins  to  germinate  its  nucleus  divides  and  its  wall 
enlarges.  Nourishment  is  absorbed  from  adjacent  tis- 
sues. Of  the  two  nuclei  formed  by  the  first  division, 
one  passes  to  each  end  of  the  embryo-sac.  The  two  nuclei 
divide  into  four,  the  four  into  eight,  four  of  these  being 
placed  at  each  end  of  the  embryo-sac.  One  from  each 
end  then  passes  to  the  central  part  of  the  sac,  and  these 
two  unite,  thus  forming  the  primary  endosperm  nucleus. 
Of  the  three  cells  remaining  nearest  to  the  micropyle  one 
is  the  egg  or  oosphere,  and  the  other  two  are  synergids 
(helpers).  At  the  opposite  end  of  the  embryo-sac  are  the 
three  antipodal  cells.  By  the  time  these  structures  are 
developed  the  embryo-sac  has  enlarged  sufficiently  to 
occupy  a  considerable  part  of  the  ovule. 
By  means  of  sections  of  ovules  within  ovaries  of  various 
ages,  locate  and  study  the  various  stages  in  the  development 
of  the  female  gametophyte.  The  following  stages  should  be 
observed: 

a.  The  relatively  large  cell,  the  megaspore.     Observe  its 
prominent  nucleus. 

b.  The  embryo-sac,  with  two  nuclei.     Observe  the  change 
in  form  in  the  old  megaspore  wall,  now  the  embryo-sac, 
and  the  positions  of  the  nuclei.     (It  is  possible  in  many 
such  preparations  to  see  the  nuclei  in  process  of  division.) 

c.  The  embryo-sac  with  four  nuclei. 

d.  The  embryo-sac  with  eight  nuclei. 

e.  Nuclei  from  each  end  (polar  nuclei)  uniting  to  form 
primary  endosperm  nucleus. 

/.  The  completed  female  gametophyte  consisting  of  seven 
nuclei,  one  of  which  is  the  egg  ready  for  fertilization. 


I$4  WAKE-ROBIN. 

g.  Make  drawings  illustrating  the  above  stages. 
5.  The  oospore  and  embryo  sporophyte.      The  microspores 
are  carried  to  the  stigma,  and  from  them  pollen-tubes  grow 
down  through  the  style  and  ovary,  and  into  the  micropyle 
of  the  ovule.     As  the  tube  pushes  its  way  through  the 
nucellus  into  the  micropylar  end  of  the  embryo-sac,1  the 
male  gametes  migrate  to  the  end.     Arrived  here  the  tip 
of  the  tube  opens,  the  male  gametes  pass  out  and  one  of 
them  unites  with  the  egg,  thus  producing  the  oospore.2 
By  means  of  sections  similar  to  those  used  in  4,  except  that 
they  are  made  from  slightly  older  ovules,  observe: 

1.  The  oospore.     Note  whether  the  synergids  are  present, 
and  whether  the  primary  endosperm  nucleus  has  begun 
to  divide  to  form  the  endosperm. 

2.  A  stage  in  which  the  oospore  has  divided  to  form  the 
embryo.     Note  the  suspensor  cell  that  attaches  the  em- 
bryo to  the  micropylar  end  of  the  sac. 

3.  A  stage  in  which  the  suspensor  has  become  considerably 
elongated,  thus  pushing  the  embryo  proper  well  into  the 
embryo-sac.     Note  the  condition  of  the  endosperm  calls 
at  this  time. 

4.  In  a  practically  mature  seed  observe  the  much  larger 
embryo   about   which   the   endosperm   cells   are   closely 
packed. 

5.  Draw,  illustrating  the  above  stages. 

By  use  of  Gray's  "Manual  of  Botany"  or  Britton's  "Flora 

1  It  has  been  shown  by  different  investigators  that  in  several  Angio- 
sperms  of  rather  low  rank  the  pollen-tubes  may  pass  through  the  basal 
(chalazal)  end  of  the  ovule  and  then  traverse  the  length  of  the  ovule 
to  its  nucellar  end,  thence  into  the  embryo-sac  in  order  to  effect  fer- 
tilization.    Such  a  condition  is  known  as  chalazogamy. 

2  The  research  work  of  the  past  few  years  indicates  that  double  fer- 
tilization is  not  uncommon  and  is  probably  the  rule  in  Angiosperms. 
It  has  been  shown  in  many  plants  that  one  of  the  male  cells  unites 
with  the  egg,  while  the  other  passes  down  to  the  primary  endosperm 
nucleus  and  unites  with  it. 


TRILLIUM  SP.  1$5 

of  the  Northeastern  States  and  Canada"  ascertain  how  one 
not  knowing  the  generic  name  of  this  plant  would  discover 
the  name  and  determine  its  classification.  Determine  for 
yourself  the  specific  name  of  the  plant  you  have  studied. 

ANNOTATIONS. 

In  its  superficial  appearance  Trillium  is  not  a  good 
representative  of  the  Monocotyledons.  Most  Monocotyle- 
dons have  parallel-veined  leaves  with  sheathing  bases, 
but  in  this  particular  Trilliums  are  quite  like  the  Di- 
cotyledons. In  flower  and  stem,  however,  it  is  a  typical 
Monocotyledon. 

In  reproductive  structures  this  plant  shows  a  distinct 
advance  over  the  pine,  in  that  there  is  here  a  true 
"flower,"  i.e.  groups  of  conspicuously  colored  leaves  as- 
sociated with  the  sporophylls.  The  calyx  in  flowers  is 
usually  protective  and  the  corolla  generally  supposed  to 
be  a  device  for  attraction  of  insects,  though  there 
are  many  cases  where  the  parts  do  not  perform  these 
functions.  The  calyx  or  even  foliage  leaves  may  do 
the  work  of  attraction.  The  ovules  (megasporangia)  are 
entirely  enclosed  by  the  carpels,  and  the  microspores 
in  pollination  are  placed  upon  the  specially  prepared  sur- 
face of  the  carpel  (stigma)  instead  of  directly  upon  the 
nucellus  as  in  the  pines.  This  necessitates  much  greater 
elongation  of  the  pollen-tube,  which  takes  place  in  much 
less  time.  In  the  pine  the  development  of  the  pollen- 
tube  is  accomplished  in  a  period  of  twelve  or  thirteen 
months,  while  in  Trillium  a  very  much  greater  distance 
is  traversed  in  a  day  or  two,  possibly  in  a  few  hours. 

In  the   pine   the   male   gametophyte  is   very   greatly 


156  WAKE-ROBIN. 

reduced,  but  in  Angiosperms  the  reduction  is  greater, 
the  male  gametophyte  consisting  merely  of  one  tube- cell 
and  two  male  cells.  These  may  form  before  the  mi- 
crospore  has  left  the  microsporangium. 

The  megaspore  is  formed  within  the  nucellus  of  the 
ovule  as  in  the  Gymnosperms,  but  its  germination  differs 
somewhat.  The  germination  of  the  megaspore  results 
in  the  formation  of  a  seven-nucleate  female  gametophyte 
consisting  of  three  antipodal  nuclei,  the  primary  endo- 
sperm nucleus,  and  the  egg  apparatus  consisting  of  an 
egg  and  two  synergids.1  Fertilization  of  the  egg  then 
occurs,  forming  the  oospore. 

The  peculiar  phenomenon  of  double  fertilization, 
already  proven  to  exist  in  many  plants  and  probable 
for  others,  offers  problems  difficult  to  solve.  Heretofore 
it  has  been  customary  to  consider  the  endosperm  as  a 
delayed  development  of  the  female  gametophyte.  The 
phenomenon  of  double  fertilization  suggests  the  possi- 
bility of  two  embryos  formed  within  the  embryo-sac, 
the  one  developing  normally  into  the  embryo  plantlet, 
while  the  other  becomes  the  endosperm  and  serves  to 
nourish  its  twin.  Further  researches  may  give  light 
upon  this  question. 

By  continuous  divisions  transverse  to  the  long  axis 
of  the  embryo-sac,  the  oospore  develops  the  several- 
celled  suspensor  and  the  cell  or  cells  known  as  the  embryo 
proper.  As  the  latter  grows,  various  parts  are  differen- 
tiated and  with  the  simultaneous  growth  of  the  ovule 
the  ripened  seed  is  formed.  After  a  period  of  rest  this 

1  The  exact  correspondence  of  these  various  structures  to  those  in 
Gyrnnosperms  and  Pteridophytes  has  not  yet  been  determined. 


TRILLIUM  SP.  157 

seed  may  "germinate"  and  produce  a  new  Trillium 
plant. 

The  root- stock  is  a  storage  region  for  surplus  foods 
and  is  a  device  for  tiding  over  unfavorable  seasons  by 
retreating  underground. 

In  the  aerial  stem  a  notable  feature  is  the  arrangement 
and  structure  of  the  vascular  bundles.  While  they 
are  not  so  well  developed  as  in  some  other  Monocotyledons 
(grasses,  corn,  oats,  etc.),  they  show  an  indefinite  distri- 
bution, and  the  closed  bundle  is  typical  of  the  group. 
Few  Monocotyledons  increase  in  thickness  by  cambial 
activity,  as  do  the  pines.  When  such  a  cambium  is  formed, 
it  does  not  increase  the  radial  dimensions  of  the  xylem 
and  phloem  already  formed,  but  gives  rise  by  tangential 
division  to  tissues  which  become  new,  isolated  bundles 
and  parenchymatous  ground  tissue  between  them. 


BUTTERCUP. 

Ranunculus  sp. 

SPERMATOPHYTES;         ANGIOSPERMS;  RANUNCULACE.E. 

PRELIMINARY. 

DURING  spring,  summer,  and  early  autumn  various 
species  of  Ranunculus  are  fairly  abundant,  especially 
along  fence-rows  in  low  grounds  and  in  and  about  woods. 
Several  species  are  sprawling  and  resemble  the  straw- 
berry plant.  The  flowers  of  some  of  the  species  are 
formed  in  water,  but  those  are  undesirable  for  this  study. 
If  the  plant  is  not  to  be  studied  at  the  time  it  is  in  flower, 
it  may  easily  be  preserved  in  sufficient  quantity  to  serve 
for  classes  of  considerable  size.  Caltha  will  serve  as 
an  excellent  substitute  for  Ranunculus,  or  any  other 
relatively  simple  Dicotyledonous  plant  may  be  used. 

LABORATORY  WORK. 

GROSS  STRUCTURE.     Compare  with  Trillium. 
I.  STEM. 

Is  the  main  stem  underground?    If  so,  compare: 

1.  Form  and  size. 

2.  Direction  of  growth. 

3.  Branching. 

4.  Buds  and  origin  of  roots. 

158 


RONUNCULUS  SP.  159 

If  all  or  some  of  the  stem  is  aerial,  compare  with  the  aerial 
stem  of  Trillium  as  to: 

5.  Form  and  size. 

6.  Position. 

7.  Nodes  and  internodes. 

8.  Branching. 

II.  ROOTS.     Compare  with  Trillium  as  to: 

1.  General  appearance. 

2.  Branching. 

3.  Number. 

III.  LEAVES.     Compare  with  Trillium  as  to: 

1.  Position  of  the  stem. 

2.  Form,  size,  and  number. 

3.  Division   into   two  regions,  the  expanded  leaf-blade,  or 
lamina,  and  the  leaf-stalk,  or  petiole. 

4.  Veining. 

5.  The  leaf  margin. 

IV.  THE  FLOWER.     Compare  with  Trillium  as  to: 

1.  The  distribution  of  flowers  over  the  stem. 

2.  Floral  organs  present. 

3.  Number  and  arrangement  of  organs  with  reference  to  or- 
gans of  other  sets. 

4.  Note  that  in  Ranunculus  the  many  carpels  are  separate, 
each  forming  a  simple  pistil. 

V.  DRAW,  showing  general  characters  of  roots,  stem,  leaves, 
and  flowers. 

MINUTE  STRUCTURE. 
I.  THE  STEM. 

Make  a  cross-section  of  the  stem  *  and  examine,  observing; 
i.  The  peripheral  region  or  cortex. 

o.  Outermost  protecting  layer  (epidermis). 
6.  Surface  hairs  and  where  they  arise. 

1  This  stem  may  be  readily  sectioned  free-hand. 


160  BUTTERCUP. 

c.  Loose  arrangement  of  the  cortical  parenchyma,  with 
intercellular  spaces. 

d.  Presence  of  chlorophyll  in  some  cells. 

2.  The  pith  region,  sometimes  hollow,  occupying  the  central 
axis  of  the  stem. 

a.  Size  and  form  of  the  cells. 

b.  Intercellular  spaces. 

c.  Relative  extent  of  pith  area. 

3.  The  vascular  bundle  region  lying  between  pith  and  cor- 
tex. 

a.  Distribution  of  the  bundles. 

6.  Parts  of  a  bundle  pair. 

i.  Phloem,  just  within  the  cortex.  Observe  the  ex- 
tent of  each  phloem  strand,  and  the  way  in  which 
the  phloem  cells  gradually  grade  into  the 
ii.  Cambium  layer,  composed  of  small  thin-walled  rect- 
angular cambium  cells.  These  actively  growing 
cells  produce  new  tissues  from  their  outer  and  in- 
ner faces  throughout  the  growing  season. 
iii.  Xylem,  composed  of  cells  whose  peculiar  thicken- 
ings can  only  be  seen  in  longitudinal  section.  In 
the  central  part  of  an  entire  section  will  be  seen  the 
xylem  ring,  outside  of  which  is  the  cambium  ring 
that  is  in  turn  surrounded  by  the  phloem  ring. 
Examine  sections  of  both  young  and  old  stems  to 
see  the  differences  in  the  amounts  of  xylem  and 
phloem  present  and  the  way  in  which  they  are 
crowded  together. 

4.  Diagram  the  regions  of  the  entire  cross-section  and  illus- 
trate in  detail  the  tissues  composing  the  older  stem. 

II.  THE  LEAF. 

If  satisfactory  results  were  obtained  in  a  study  of  the  leaf 
of  Trillium,  the  study  may  here  be  omitted.  Otherwise  use 
the  leaf  outline  given  under  that  plant. 


RANUNCULUS  SP.  16* 

III.  THE  FLOWERS. 

By  using  specially  prepared  slides,  make  a  careful  study  and 
comparison  with  similar  structures  in  Trillium  as  follows: 

1.  The  development  of  the  microspores. 

2.  The  first  stages  in  the  germination  of  the  microspores. 

3.  The  development  of  the  megaspore. 

4.  The  germination  of  the  megaspore  and  production  of  the 
female  gametophyte. 

5.  The  development  of  the  sporophyte  embryo. 

IV.  CLASSIFICATION. 

By  consulting  Gray's  or  Britton's  Manual  used  in  con- 
nection with  Trillium: 

1.  Trace  in  the  key  to  genera  in  the  family  Ranunculacea l  the 
genus  Ranunculus. 

2.  Determine  the  species  of  Ranunculus  that  you  have  studied. 

ANNOTATIONS. 

This  plant  serves  as  an  illustration  of  the  group  of 
Angiosperms  known  as  Dicotyledons,  and  offers  some 
comparisons  with  the  Monocotyledon  last  studied.  The 
leaves  are  petioled,  net- veined,  and  "open"  at  the 
margin;  i.e.  the  veins  end  in  the  margin  of  the  leaf,  and 
are  not  parallel  and  ending  at  the  tip  of  the  leaf  as  in 
the  closed  Monocotyledon  leaves.  It  must  be  borne 
in  mind  that  in  the  veining  Trillium  is  not  like  most 
Monocotyledons.  In  that  feature  the  corn  plant  or 
lily  affords  better  illustration  of  the  group  characteristics. 

The  stem  of  Ranunculus  has  its  vascular  bundles  so 
distributed  as  to  form  a  hollow  cylinder,  all  the  xylem 
strands  being  next  the  pith,  the  phloem  strands  next 
the  cortex,  and  the  cambium  strands  between  the  two. 

1  For  any  terms  unknown,  see  glossary  in  either  book  cited. 


162  BUTTERCUP. 

Such  an  arrangement  makes  possible  the  increase  in 
diameter  of  Dicotyledonous  plants  throughout  the  grow- 
ing season.  In  perennial  trees  or  shrubs  this  increase 
takes  place  annually,  as  is  shown  by  the  so-called  "  annual 
rings."  The  strong  supporting  shafts  of  our  trees  are 
due  chiefly  to  the  great  development  of  the  xylem  bundles. 
In  Dicotyledons  underground  stems  of  all  kinds  are 
less  common  than  in  Monocotyledons;  while  distinctly 
fibrous  roots,  and  tap-roots  with  secondary  root  systems, 
are  the  usual  subterranean  organs. 

The  flower  of  Ranunculus  is  a  relatively  simple  one. 
The  carpels  are  numerous  and  separate,  each  carpel 
here  forming  a  separate  pistil.  The  stamens  are  numerous 
and  spirally  arranged.  Numerous  carpels  and  stamens, 
and  spiral  arrangement  of  floral  organs,  are  characteristic 
of  the  simpler  Dicotyledons.  The  placing  of  the  other 
floral  organs  below  the  ovary  (hypogynous  arrangement) 
is  also  indicative  of  the  lower  members  of  the  group. 

The  classification  of  Ranunculus  in  the  manual  should 
be  done  with  the  idea  of  learning  how  to  study  the  classi- 
fication of  plants  rather  than  with  the  idea  that  an  exten- 
sive work  in  classification  is  to  be  done  in  this  course.1 

1See"A  contribution  to  life-history  of  Ranunculus,"  by  John  M. 
Coulter,  Bot.  Gaz.  25  :  73-88. 


SHEPHERD'S-PURSE.' 

Capsella  bursa-pastoris. 

SPERMATOPHYTES;         ANGIOSPERMS;  CRUCIFERxE. 

PRELIMINARY. 

THE  plant  is  of  European  origin,  but  has  become 
abundant  in  this  country  and  elsewhere,  being  one  of 
those  vigorous  foreign  species  that  hasten  to  take  posses- 
sion of  any  cleared  or  cultivated  land.  It  is  found 
everywhere  around  dwellings,  and  in  fields  and  waste 
grounds.  It  has  not  only  the  advantage  of  universal 
distribution,  but  also  of  continuous  growth  most  of 
the  year,  even  a  few  warm  days  in  winter  calling  it  into 
bloom. 

1  If  toward  the  end  of  the  course  there  is  sufficient  time,  it  will 
be  found  helpful  after  completing  this  and  the  following  exercise  to 
carry  on  a  series  of  studies  of  plants  representative  of  the  leading  plant 
families,  especially  in  the  Angiosperms.  This  outline  of  "Shepherd's- 
purse"  will  suggest  the  kind  of  work  to  be  done  in  such  studies.  It  is 
understood  that  in  most  cases  the  students  will  not  know  the  plant 
studied,  and  consequently,  at  the  same  time  that  they  are  studying  the 
representatives  of  a  plant  family,  they  will  also  obtain  some  practice 
in  determining  the  classification  of  plants.  It  is  suggested  that  rep- 
resentatives be  selected  from  such  families  as  the  Araceac,  Gramineae 
Salicaceae,  Rosaceae,  Malvaceae,  Balsamineae,  Leguminosae,  Euphorbia- 
ceae,  UmbelUferss,  Solanaceae,  and  Convolvulaceae. 
163 


1 64  SHEPHERD'S-PURSE. 

When  not  flowering,  the  plant  consists  of  a  rosette  of 
notched  leaves  lying  flat  upon  the  ground.  From  this 
rosette  there  arises  a  flowering  stalk  upon  which  are 
a  few  scattered  leaves  and  the  many  small  white  flowers. 
The  seed-pods  are  triangular  heart-shaped  structures 
that  serve  well  to  distinguish  the  plant  from  all  others. 
The  plant  is  most  abundant  in  spring  and  early  summer, 
but  can  be  found  in  bloom  throughout  the  warm  months, 
and  may  be  quite  readily  grown  in  the  greenhouse  for 
winter  use. 

In  order  to  study  the  leading  family  characters  as 
shown  by  this  plant  and  to  determine  its  classification 
only  gross  structures  need  be  considered. 


LABORATORY   WORK. 

I.  THE  PLANT  BODY.    Observe: 

1.  The  main  root  from  which  arise 

2.  The  secondary  roots. 

3.  The  stem  and  its  branches. 

4.  The  leaves. 

a.  The  rosette  leaves,  their  general  position,  and  their 
arrangement  enabling  all  or  nearly  all  to  receive  light. 

b.  The  leaves  on  the  upright  stem,  their  form  and  size  as 
compared  with  the  rosette  leaves.     Note  the  differences 
in  leaves  on  different  parts  of  the  stem. 

II.  THE  FLOWERS.    Observe: 

1.  Calyx;  size,  form,  and  number  of  sepals. 

2.  Corolla;  size,  form,  and  number  of  petals.    Are  they  alter- 
nate or  opposite  the  sepals  ? 

3.  Stamens;   size  and  relative  length;   number  of  cycles  of 


CAP  SELL  A   BVRSA-PASTORIS.  165 

stamens  and  number  in  each  cycle.    Are  they  alternate 
or  opposite  the  petals? 

4.  Carpels  or  pistils. 

a.  Parts  of  pistil;  ovary,  style,  and  stigma. 

b.  Number  of  chambers  or  cells  in  the  ovary,  as  determined 
by  a  cross-section  of  it. 

5.  Whether  flowers  are  hypogynous,  perigynous,  or  epigynous. 

m.  THE  SEED-POD.    Observe: 

1.  The  general  form. 

2.  The  midrib  dividing  it  into  two  parts. 
By  dissecting  it,  observe: 

3.  The  seeds  (ovules),  their  number  and  how  they  are  placed 
in  the  pod. 

4.  By  use  of  manuals,  beginning  with  the  analytical  key,  de- 
termine the  family,  genus,  and  species  of  this  plant. 

ANNOTATIONS. 

This  plant  has  well-marked  generic  and  specific  char- 
acteristics. The  leaves  are  distinctly  notched,  the  basal 
ones  being  arranged  into  a  rosette.  This  rosette  persists 
through  rather  unfavorable  seasons,  and  shows  interest- 
ing adjustments  in  form  and  position  to  insure  adequate 
exposure  to  the  light.  The  leaves  on  the  stem  are 
younger  and  are  small,  sessile,  and  constantly  smaller  as 
they  approach  the  top  of  the  plant,  probably  doing  but 
a  small  part  of  the  plant's  chlorophyll  work. 

The  main  root  is  strong  and  serves  as  a  storehouse 
for  surplus  food,  thus  enabling  the  aerial  organs  to  make 
rapid  growth  when  conditions  are  favorable.  Secondary 
roots  arise  from  this  primary  one. 

The  flowers  are  small,  the  tetradynamous  character 


1 66  SHEPHERD'S-PURSE. 

of  the  stamens  being  a  striking  feature.  Four  sepals, 
four  petals,  six  stamens,  and  the  flattened  ovary  more  or 
less  clearly  divided  into  two  parts  serve  as  an  excellent 
illustration  of  the  leading  floral  characteristics  in  the  fam- 
ily Cruciferae. 


SUNFLOWER. 

Helianthus  annuus. 

SPERMATOPHYTES;        DICOTYLEDONS;  COMPOSITE. 

PRELIMINARY. 

THIS  plant  belongs  to  the  Composite,  which  is  the 
highest  family  of  the  plant  kingdom.  It  is  so  universally 
recognized  that  no  general  description  is  needed.  The 
species  mentioned  is  the  most  common  of  the  cultivated 
sunflowers,  but  any  wild  species  will  serve  well  for  the 
study.  In  case  it  is  not  convenient  to  obtain  any  of  the 
species  of  this  genus,  there  are  numerous  representatives 
of  the  Compositae  that  are  good  illustrations  of  the  group. 
The  rosinweed  (Silphium),  coneflower  (Rudbeckia),  gold- 
enrod  (Solidago),  ox-eye  daisy  (Chrysanthemum},  and  dan- 
delion (Taraxacum),  suggest  the  members  of  the  family 
that  may  be  selected.  If  the  study  is  to  be  made  at  a 
time  when  fresh  specimens  are  not  available  either  in  the 
field  or  greenhouse,  preserved  material  may  be  used, 
though  the  use  of  such  material  will  rarely  be  necessary. 
167 


1 68  SUNFLOWER. 


LABORATORY  WORK. 

GROSS  STRUCTURE.1 

I.  THE  PLANT  BODY.     Observe: 

1.  General  arrangement  of  parts,  especially: 

a.  Number  of  leaves. 

b.  Size  of  leaves  and  length  of  petioles. 

c.  Arrangement  of  leaves  on  the  stem  in  order  to  secure 
proper  exposure  to  light. 

d.  The  changes  throughout  the  day  in  position  of  the  tip 
of  a  plant.     What  function  is  served  by  the  change? 

2.  The  stem.     Observe: 

a.  The  supporting  strength. 

b.  The  hairs  of  the  surface. 

c.  In  a  transverse  section  observe: 

i.  The  central  pith  tissue, 
ii.  The  strengthening  tissue. 

3.  The  leaf.     By  means  of  surface  mounts  of  the  epidermis 
and  cross-sections  of  the  leaf  observe: 

a.  The  epidermal  hairs;   their  abundance. 

b.  The  number  and  distribution  of  stomata  as  compared 
with  those  of  leaves  already  studied. 

c.  The  thickness  of  the  cuticle,  and  the  epidermal  protec- 
tion furnished  to  the  stomata. 

d.  Make  drawings  illustrating  any  structures  of  this  leaf 
not  seen  previously. 

1  In  Helianthus  as  well  as  in  the  entire  family  Compositae  the  detailed 
structures  of  the  stem,  leaf,  and  roots,  and  those  that  have  to  do  with 
the  embryo-sac,  fertilization,  and  seed  formation,  are  essentially  like 
those  already  examined  in  other  Angiosperms.  Consequently  the  out- 
line does  not  provide  for  work  in  these  parts.  The  composite  inflores- 
cence, however,  offers  certain  peculiar  advantages  for  study  of  progres- 
sive stages  in  the  development  of  floral  structures. 


HELIANTHUS  ANNUUS.  169 

II.  THE  INFLORESCENCE. 

The  head  consists  of  a  number  of  more  or  less  modified 
flowers  borne  on  a  common  receptacle.  The  outer  ones  usually 
have  their  corollas  very  prominent,  and  distinctly  unlike  the 
corollas  of  the  inner  flowers.  Observe: 

1.  The  involucre,  consisting  of  green  leaf -like  organs  or  bracts 
that  enclose  the  base  of  the  head.     Observe: 

a.  The  number  of  cycles  of  bracts. 

b.  The  way  in  which  they  enclose  young  heads. 

2.  The  ra^-flowers,  the  outer  ring  of  flowers.     Observe: 

a.  The  prominent  yellow  corolla,  tubular  at  base  and  flat- 
tened above.     The  notched  tips  of  these  corollas  are 
taken  to  indicate  the  number  of  petals  that  the  united 
structure  represents. 

b.  The  carpel  with  prominent  style  and  stigma,  on  whose 
base  (ovary)  the  epigynous  corolla  seems  to  be  borne. 

c.  The  absence  of  stamens. 

3.  The  disk-flowers,  those  occupying  the  part  of  the  recep- 
tacle surrounded  by  the  ray-flowers.     Remove  a  few  of 
the  flowers  and  observe: 

a.  The  distinctly  tubular  corolla  with    five-toothed    rim 
(see  2  a  above),  supported  by 

b.  The  elongated  ovary.     Extended  from  the  mouth  of  an 
older  corolla  is 

c.  The  two-parted  style  and  its  stigmas. 

Open  the  corolla  of  a  rather  young  disk-flower  and  observe: 

d.  The  stamens  with  their  anthers  joined,  thus  forming  a 
tube  that  adheres  closely  around  the  style  (syngenesi- 
ous). 

By  studying  young  and  old  disk-flowers  observe: 

e.  How  the  style  elongates,  forcing  its  tip  up  through  the 
stamen-ring. 

Mount  the  stigmatic  end  of  the  style  and  observe: 
/.  The  pollen-grains  upon  it. 


170  SUNFLOWER. 

g.  The  hairs  by  which  they  are  held. 

h.  Try  to  determine  whether  these  flowers  are  necessarily 
self-pollinated,  by  finding  whether  pollen  is  ready  to  be 
shed  at  the  time  the  stigma  is  ripe,  and  by  finding 
whether  the  position  of  parts  favors  self-pollination  or 
cross-pollination. 

i.  Draw  the  disk -flowers. 

ANNOTATIONS. 

In  the  lowest  group  of  Angiosperms  the  flowers  are 
hypogynous,  the  floral  organs  are  numerous,  and  the 
flowers  are  scattered.  In  higher  groups  there  is  a  con- 
stant tendency  toward  perigynous  (corolla  around  the 
ovary)  and  epigynous  (corolla  above  or  upon  the  ovary) 
flowers,  and  also  toward  a  relatively  small  and  regular 
number  of  floral  organs  in  each  set.  Some  groups 
lower  than  Compositae  have  attained  epigyny  and  definite 
numbers,  and  the  Umbelliferae  (one  of  the  highest  family 
of  Dicotyledons)  have  approached  the  Composite  inflor- 
escence, but  this  feature  in  its  highest  expression  is  the 
distinguishing  characteristic  of  this  great  group.  The 
form  of  inflorescence  makes  possible  the  production  of 
many  flowers  upon  a  relatively  small  area. 

The  structures  of  the  plant  body  of  Helianthus  indicate 
some  of  the  excellent  adaptations  to  environment  so 
common  in  Compositae,  though  by  no  means  peculiar  to 
this  family.  The  plant  is  especially  well  adapted  to 
living  in  regions  of  great  exposure  to  light  and  heat. 

In  Helianthus  the  flowers  are  divided  distinctly  into 
ray  and  disk  flowers.  The  ray-flowers  are  devoid  of 
stamens,  and  are  given  over  entirely  to  serve  as  showy 


HELIANTHUS  ANNUUS.  171 

organs  for  the  entire  group,  no  seeds  even  being  ripened 
within  the  ovaries  of  these  flowers.  The  seeds  are  formed 
in  the  disk-flowers,  one  seed  forming  in  each  ovary.  These 
conditions  do  not  obtain  for  all  Composite,  however.  In 
some,  such  as  the  dandelion  (Taraxacum),  all  the  flowers 
are  like  ray-flowers;  while  in  some  others,  such  as  the  yar- 
row (Achillea  millejolium) ,  all  are  tubular  disk-flowers.  In 
some,  such  as  the  rosinweed  (Silphium)  the  ray-flowers 
mature  seeds,  although  they  have  no  stamens. 

The  Composite  are  remarkably  successful  as  a  group, 
being  abundantly  distributed  almost  everywhere  during 
summer  and  autumn.  They  probably  constitute  the 
youngest  and  most  successful  group  of  plants. 


GLOSSARY.* 

Abstriction  (act  of  unbinding).  Partial  or  complete  separation 
by  contraction. 

Achlorous   (without  green).     Devoid  of  chlorophyll. 

Alternation  of  generations.  The  alternation  of  gametophyte 
and  sporophyte.  Each  produces  a  spore  that  upon  ger- 
mination produces  the  other  generation,  thus  completing 
the  life-cycle. 

Anatropous  (turned  up).  Said  of  an  inverted  ovule  or  seed 
which  has  the  raphe  extending  its  whole  length. 

Androecium  (male  household).  The  stamens  of  a  flower  col- 
lectively; the  name  was  applied  at  a  time  when  it  was 
supposed  that  stamens  were  male  sex-organs. 

Anemophilous  (wind-loving).  Applied  to  plants  that  use  the 
wind  as  a  means  of  pollination. 

Annulus  (a  ring).  The  elastic  ring  of  cells  around  the  sporan- 
gium in  ferns. 

Anther  (flowery).     The  pollen-bearing  part  of  the  stamen. 

Antheridium,  pi.  antheridia  (anther  form).  The  male  sex- 
organ  of  the  lower  groups  of  plants. 

Antherozoids.     See  Sperm. 

Antipodal  (against  the  foot).  Said  of  a  group  of  cells  at  the 
end  of  the  embryo-sac  farthest  from  the  micropyle. 

Apetalous  (without  petals).  Applied  to  flowers  that  are 
devoid  of  specialized  floral  leaves. 

Apical.     At  the  apex  or  tip. 

Apocarpous  (without  carpels).  Applied  to  flowers  in  which  the 
carpels  are  entirely  free  from  one  another. 

Apophysis  (an  offshoot).  In  mosses,  an  enlargement  of  the 
pedicel  at  the  base  of  the  capsule. 

*  In  connection  with  most  of  the  terms  included  in  the  glossary  there  are  given  in 
parenthesis  suggestions  as  to  the  original  meaning  of  terms.  In  many  cases  such 
insertions  help  materially  in  understanding  the  terms  as  they  are  used  in  botany. 

173 


174  GLOSSARY. 

Archcgonium,   pi.    archegonia    (beginning    of   offspring).     The 

female  organ  of  Bryophytes  and  Pteridophytes. 
Archesporium    (beginning  of  a   seed).     The   cell   or  group   of 

cells  that  initiates  the  spore-producing  series. 
Areola,  pi.  areolce  (a  small  open  space) .     The  spaces  in  a  reticu- 
lated surface,  as  in  the  thallus  of  Marchantia. 
Ascocarp  (ascus  fruit).     The  specialized  body  in  which  asci  are 

formed. 

Ascos pores  (ascus  seeds).     The  spores  formed  in  an  ascus. 
Ascus,  pi.  asci  (a  sac  or  bag).      The  spore-sac  of  a  large  group 

of  Fungi. 
Asexual  spore.     A  spore  formed  entirely  independent  of  any 

cell  union. 

Axial.     Relating  or  belonging  to  the  axis. 
Axil  (the  armpit).     The    angle  just    above  the  attachment  of 

a  leaf  to  the  stem. 
Axis  (the  pole).     The  central  part  or  longitudinal  support  on 

which  organs  or  parts  are  arranged. 
Bast.     In  general,  the  phloem  region  of  a  fibro- vascular  bundle; 

or,  specifically,  the  fibres  of  the  phloem. 
Bract  (a  thin  plate).     The  more  or  less  modified  leaves  of  a 

flower-cluster. 
Bryophyta  (moss-plants).     A  primary  division  of  plants,  named 

from  its  principal  group,  the  mosses.      Bryophyte  is  the 

English  equivalent. 
Callus  (hard  skin) .     A  hardened  or  thickened  place ;  technically 

used  of  the  thickening  mass  in  a  sieve-plate,  usually  ap- 
pearing as  a  layer  on  each  side  of  the  plate. 
Calyptra   (a  cover).     In  mosses,   the  hood  which  covers  the 

capsule. 
Calyx  (a  cup).     The  outer  envelope  of  a  flower,  composed  of 

sepals. 

Cambiform.     Resembling  cambium. 
Cambium  (exchange).     The  meristem  cells  of  a  fibro- vascular 

bundle,    lying    between    the    phloem    and    xylem,    which 

retain  the  power  of  division. 
Campylotropous  (turned  or  curved).     Said  of  an  ovule  or  seed 

which  becomes  curved  in  its  growth  so  as  to  be  inverted. 
Capsule  (a  small  box).     A  dry  dehiscent  seed-vessel  (formed  of 

more  than  one  carpel) ;    or  a  similar  spore- vessel. 
Carpel   (fruit).     The   megasporophyll;     hence   either  a   simple 

pistil,  or  one  of  the  parts  of  a  compound  pistil. 


GLOSSARY.  175 

Carpellary.     Relating  to  a  carpel. 

Carpophyta     (fruit-plants).     A    primary     division    of    plants, 

named  from  the  sporocarp,  or  spore- vessel,  which  is  the 

result  of  fertilization.      Carpophyte  is  the  English  equiv- 
alent. 

Caulicle  (a  small  stem).     The  initial  stem  in  an  embryo. 
Cell.     The  anatomical  unit  of  plant-structure. 
Cellulose  (pertaining  to  a  cell).     The  primary  substance  of  the 

cell-wall. 

Chaff.     Small  dry  scales. 
Chalaza  (a  pimple  or  tubercle).     The  part  of  an  ovule  where 

integuments  and  nucellus  are  confluent. 
Chlorophyceae  (green  seaweeds) .     The  green  Algae. 
Chlorophyll  (leaf-green).     The  green  coloring-matter  of  plants. 
Cilium,    pi.    cilia    (eyelash).     Marginal    hairs;     motile    proto- 
plasmic filaments,  as  those  of  sperms. 

Closed  bundle.     A  fibro- vascular  bundle  containing  no  cambium. 
Ccenocyte.     A  number  of  nucleated  masses  of  cytoplasm  (cells) 

enclosed  within  a  common  wall. 
Collateral    (sides   together).     Side   by   side;     used   of   a   fibro- 

vasctilar  bundle  in  which  the  xylem  and  phloem  are  side 

by  side  in  a  radial  direction. 
Columella   (a  small  column).     The  persistent  axis  of  certain 

spore-cases,  as  in  mosses. 
Concentric    (center    together).     Technically    used    of    a    fibro- 

vascular  bundle  whose  tissues  are  arranged  concentrically. 
Conidiophore  (conidium-bearer) .     The  stalk  upon  which  conidia 

are  borne. 
Conidium,  pi.  conidia  (offspring-former).     The  asexual  spores  of 

certain  groups. 
Conjugation   (joined   together).     The  sexual  union   of  similar 

gametes,  as  in  the  Conjugatae. 
Connective.     The  portion  of  the  stamen  connecting  the  parts 

of  the  anther. 
Corolla  (a  small  crown).     The  inner  envelope  of  a  flower,  within 

the  calyx,  and  composed  of  petals. 
Cortex.     The  rind  or  bark. 
Cortical.     Relating  to  the  cortex  or  bark. 
Cotyledon    (a    cup-shaped    cavity).     A    primary    embryo-leaf 

borne  by  the  caulicle. 
Cryptogams  (hidden  marriage).     A  term  used  to  include  Thallo- 

phytes,  Bryophytes,  and  Pteridophytes. 


1 76  GLOSSARY. 

Cupule  (a  little  cup).     The  gemma-cup  of  liverworts. 
Cuticle    (the    skin).     The    outermost    layer   of   the  epidermis, 

differing  chemically  from  the  remainder  of  the  cell- wall. 
Cyanophyceae   (blue  seaweeds).     A  group  of    Algae  commonly 

known  as  blue-green  Algae. 
Cyclic.     Applied  to  an  arrangement  of  leaves  or  floral  organs 

in  which  two  or  more  appear  upon  the  axis  at  the  same 

level,  forming  a  cycle  or  whorl. 

Cystocarp  (bladder-fruit) .     The  spore- fruit  of  some  Thallophytes. 
Dehiscence  (gap  or  opening).  The  opening  of  an  organ  to  discharge 

its  contents,  as  in  the  case  of  anthers,  sporangia,  capsules,  etc. 
Dermatogen  (skin-producer).     The  layer  of  nascent  epidermis 

in  the  meristem  of  growing  points. 

Dichotomous  (cutting  in  two).     Forking  regularly  by  pairs. 
Dicotyledonous  (cotyledons  double).     Having  two  cotyledons, 

or  seed-leaves. 
Dioecious    (two    households).     Having     the     two     sex-organs 

borne  by  separate  individuals. 
Dorsiventral.    Having  the  two  surfaces  differently  arranged  with 

reference  to  the  surroundings  to  which  they  are  exposed. 
Elater   (a  driver,  or  hurler).     Spirally  thickened  cells  within 

the  sporogonia  of  some  liverworts,  which  assist  in  expelling 

the  spores;     also    special  spore-distributing  structures  in 

Equisetum. 

Egg,  or  oosphere.     The  female  gamete. 
Egg-apparatus.     A  group  of  three  cells  consisting  of  the  egg 

and  two  synergids  that  lie  at  its  sides. 
Embryo  (fetus,  or  beginning  of  a  new  individual).     The  young 

plantlet  within  the  seed. 
Embryo-sac.     The  cavity,  within  the  nucellus,  in  which  the 

embryo  develops. 
Endodermis  (within  the  skin).     The  layer  of  cells  inclosing  the 

fibro- vascular  bundle;    the  bundle-sheath. 
Endogenous     (produced    within).     Originating    from    internal 

tissues,  and  penetrating  the  outer  ones. 
Endosperm     (within     the     seed).     A     parenchymatous     tissue 

developed  within  the  embryo-sac. 
Endosperm  nucleus.     The  nucleus  formed  in  the  Angiosperm 

embryo-sac  by  the  union  of  two  polar  nuclei,  one  from 

each  end  of  the  embryo-sac. 

Endospore  (within  the  spore).     The  inner  layer  of  a  spore- wall. 
Endothecium  (within  the  case).     The  inner  wall  of  the  theca.. 


GLOSSARY.  177 

Entomophilous  (insect-loving).      Applied  to  those  plants  that 

use  insects  as  means  of  effecting  pollination. 
Epidermis   (upon   the  skin).     The  outermost  layer  of  special 

cells  covering  plant-surfaces. 
Epigynous  (upon  the  ovary).     Applied  to  those  flowers  whose 

outer  parts  appear  to  arise  from  the  top  of  the  ovary. 
Epiphragm  (a  covering  or  lid).     In  mosses,  a  membrane  cover- 
ing the   orifice  of  the  capsule. 
Eusporangiate  (well  or  strong  vesseled) .     Applied  to  those  plants 

whose  sporangia  arise  from  two  or  more  hypodermal  cells. 
Exogenous  (produced  outside).     Originating  from  outer  layers 

of  tissue. 

Exospore  (outside  the  spore).     The  outer  layer  of  a  spore- wall. 
Extine  (on  the  outside).     The  outer  coat  of  a  pollen-spore. 
Fertilization.     The  act  of  union  of  the  sperm  and  the  egg. 
Fiber.     A  long  and  slender,  thick-walled  cell. 
Fibrous.     Composed  of  fibers. 
Fibro- vascular  (fiber-vessels).     Composed  of  fibers  and  vessels; 

fibro-vascular  bundles  are  the  strands  which  make  up  the 

framework  of  the  higher  plants. 
Filament  (a  thread).     The  stalk  of  the  stamen,  supporting  the 

anther;    also  the  individxial  threads  of  Algae  or  Fungi. 
Fission  (splitting).     Cell-division  that  includes  the  wall  of  the 

old  cell. 
Flowering  glume.     In  grasses,  the  bract  which  subtends  each 

flower,  sometimes  called  lower  palet. 
Foot.     A  part  of  the  sporophyte  specially  set  apart  for  the 

purpose  of  absorbing  nourishment. 
Frond  (a  leaf).     A  name  given  to  the  leaves  of  ferns. 
Fundamental  tissue.     That  outside  the  fibro-vascular  bundles 

and  inclosed  by  the  epidermis,  but  not  a  part  of  either. 
Funiculus  (a  slender  rope).  The  stalk  of  an  ovule  or  seed. 
Gametangium  (gamete  vessel).  The  specialized  organ  for 

production  of  gametes. 

Gamete.     A  reproductive  cell  which  ordinarily  becomes  func- 
tional   only    upon    union    with    another,    through    which 

union  a  sexual  spore  is  formed. 
Gemma,    pi.    gemma    (a   bud).     In    Bryophytes,    many-celled 

bodies  specialized  for  asexual  propagation. 
Generative  cell.     The  cell  within  the  male  gametophyte  (usually 

within    the  microspore-wall)   which  divides  to  form  the 

two  male  cells. 


3  7^  GLOSSARY. 

Glaucous  (pale  green,  gray).  Whitened  with  a  bloom,  like 
that  on  a  cabbage-leaf. 

Glume  (a  husk).  A  chaff-like  bract  belonging  to  the  inflores- 
cence of  grasses;  the  outer  glumes  subtend  the  spike- 
let;  the  flowering  glume  is  the  bract  of  the  flower. 

Gluten  (glue).  A  term  used  for  the  glue-like  products  of 
plants,  especially  of  seeds. 

Grain.  A  seed-like  fruit,  like  those  of  grasses,  with  pericarp 
adnate  to  the  seed;  also  any  small  rounded  body,  as  of 
starch  or  chlorophyll. 

Growing  point.  The  group  of  meristem  cells  at  the  growing 
tip  of  an  organ,  from  which  the  various  tissues  arise. 

Gynaecium  (female  household).  The  pistil  or,  collective,  pistils 
of  a  flower. 

Haustorium,  pi.  haustoria  (drinking-organs) .  The  absorbing- 
organs  of  certain  parasitic  plants. 

Hermaphrodite  (both  male  and  female).  Having  both  kinds  of 
sexual  organs  borne  together  on  the  same  axis. 

HeterogamousJ  (having  unlike  gametes).  Applied  to  plants 
whose  pairing  gametes  are  dissimilar. 

Heterosporous  (having  unlike  spores).  Applied  to  plants  in 
which  the  sporophyte  produces  two  kinds  of  asexual 
spores. 

Homosporous  (having  similar  spores).  Applied  to  plants  in 
which  the  sporophyte  produces  but  one  kind  of  asexual 
spore. 

Host.  The  plant  upon  which  parasitic  plants  (or  organisms) 
develop,  and  from  which  they  derive  their  nourishment. 

Hygroscopic  (moisture-seeing).     Having  an  avidity  for  water. 

Hymenium  (a  membrane).  In  Fungi,  a  surface  layer  of  vertical 
filaments  containing  or  bearing  spores. 

Hypha,  pi.  hyphcz  (a  web).  The  slender  vegetative  filaments 
of  Fungi  which  may  or  may  not  be  woven  into  a  mat 
(mycelium),  or  a  plant -body. 

Hypoderma  (under  the  skin).  The  thick- walled  tissues  beneath 
the  epidermis,  which  serve  to  strengthen  it,  but  do  not 
belong  to  the  fibro-vascular  bundle. 

Hypogynous  (being  under  the  ovary).  Applied  to  those 
flowers  whose  parts  are  at  or  below  the  base  of  the  ovary. 

Incumbent  (leaning  or  resting  upon).  Said  of  cotyledons,  when 
the  radicle  is  against  the  back  of  one;  of  anthers,  when 
they  lie  against  the  inner  face  of  the  filament. 


GLOSSARY.  179 

Indusium,  pi.  indusia  (clothing).  In  ferns,  a  cellular  outgrowth 
of  the  leaf  covering  the  clusters  of  sporangia  (sori). 

Inflorescence  (flowering).  The  arrangement  of  flowers;  or  the 
flowering  portion  of  a  plant. 

Integument  (covering).     The  covering  of  the  ovule. 

Intercellular.     Between  or  among  the  cells. 

Internode.     The  part  of  a  stem  between  two  nodes. 

Intine  (on  the  inside).     The  inner  coat  of  a  pollen-spore. 

Involucre  (rolled  within).  The  leaf-like  or  bracteate  set  of 
organs  that  incloses  a  cluster  of  flowers. 

Isogamous  (equal  gametes).  Applied  to  those  plants  whose 
pairing  gametes  are  similar. 

Lamina  (a  layer).  The  blade,  or  expanded  part,  of  a 
leaf. 

Leaf-trace.  The  fibro-vascular  bundles  from  the  leaf  which 
descend  into  the  stem,  and  sooner  or  later  become  blended 
with  its  fibro-vascular  system. 

Leptosporangiate  (slender- vesseled).  Applied  to  those  plants 
whose  sporangia  arise  from  one  superficial  cell. 

Ligule  (a  small  tongue).  In  grasses,  a  thin  appendage  at  the 
junction  of  leaf-blade  and  sheath. 

Lodicule  (a  small  coverlet).  A  small  scale  in  the  flower  of 
grasses. 

Medullary  (belonging  to  the  marrow).  Relating  to  the  pith; 
medullary  rays  are  the  pith-rays  which  pass  outward  to 
the  bark  between  the  fibro-vascular  bundles. 

Megaspore,  or  Macrospore  (great  or  large  spore).  The  larger 
one  of  the  two  kinds  of  asexual  spores  produced  by  certain 
Pteridophytes  and  all  Spermatophytes. 

Megasporangium  (large  spore- vessel).  The  sporangium  that 
produces  the  megaspores. 

Megasporophyll  (large  spore-leaf).  The  leaf  upon  which  the 
megasporangium  develops. 

Meristem  (dividing  tissue) .  Tissues  in  a  nascent  or  differentiat- 
ing state. 

Mesophyll  (middle  leaf).  The  green  or  soft  tissue  of  a  leaf, 
supported  by  the  framework  and  exclusive  of  the  epider- 
mis, called  by  the  older  botanists  parenchyma. 

Micropyle  (small  gate).  The  opening  left  by  the  integuments 
of  the  ovule,  and  which  leads  to  the  nucellus. 

Microsporangium  (small  spore- vessel) .  The  sporangium  that 
produces  the  microspore. 


i8o  GLOSSARY. 

Microspore  (small  spore).  The  smaller  spore  of  the  two  kinds 
produced  by  certain  Pteridophytes  and  all  Spermatophytes. 

Microsporophyll  (small  spore-leaf).  The  leaf  upon  which  the 
microsporangium  is  borne. 

Midrib.     The  central  or  main  rib  of  a  leaf  or  thallus. 

Monoecious  (one  household) .  Applied  to  those  plants  upon  one  of 
which  both  kinds  of  gametes  are  borne.  Strictly  speaking, 
the  term  applies  only  to  the  gametophyte  stage  of  plants. 

Monopodial  (having  one  foot).  Said  of  a  stem  consisting  of  a 
single  and  continuous  axis  (footstalk). 

Mutualism.  A  symbiotic  relationship  where  the  organisms  are 
mutually  helpful. 

Mother-cell.  A  cell  that  produces  new  cells  (usually)  by  internal 
division. 

Mycelium  (Fungus  growth).  The  filamentous  vegetative  growth 
of  Fungi,  composed  of  hyphae. 

Naked.     Wanting  some  usual  covering. 

Nectary.     The  place  or  appendage  in  which  nectar  is  secreted. 

Nerve.     A  simple  vein  or  rib. 

Node  (a  joint) .     That  part  of  a  stem  which  normally  bears  leaves. 

Nucellus  (a  little  kernel).  The  mass  of  the  ovule  within  the 
integuments. 

Nucleolus  (diminutive  of  nucleus) .  The  sharply  defined  rounded 
part  often  seen  in  the  nucleus. 

Nucleus  (a  kernel).  The  usually  roundish  mass  found  in  the 
protoplasm  of  most  active  cells,  and  differing  from  the 
rest  of  the  protoplasm  in  its  greater  densit)*-. 

Oogonium,  pi.  oogonia  (egg-offspring).  The  female  organ  of 
Thallophytes. 

Oophyta  (egg-plants).  A  primary  division  of  plants,  named 
from  the  mode  of  reproduction,  the  egg-spore  plants. 

Oophyte  is  the  English  equivalent  of  Oophyta. 

Oosphere  (egg-sphere).  The  female  egg-cell;  the  mass  of 
protoplasm  prepared  for  fertilization. 

Oospore  (egg-spore).     The  egg-cell  after  fertilization. 

Open  bundle.     A  fibre-vascular  burdle  which  contains  cambium. 

Operculum,  pi.  opercula  (a  cover  or  lid).  In  mosses  the  ter- 
minal lid  of  the  capsule. 

Ovary  (egg-keeper).  That  part  of  the  carpel  which  contains 
the  ovules. 

Ovule  (an  egg).  The  body  which  becomes  a  seed  after  fertili- 
zation and  maturation. 


GLOSSARY.  181 

Palet  (chaff).     In  grasses,  the  inner  bract  of  the  flower. 

Palisade  cells.  The  elongated  parenchyma  cells  of  a  leaf,  which 
stand  at  right  angles  to  its  surface,  and  are  often  con- 
fined to  the  upper  part. 

Palmate  (pertaining  to  the  hand.)  Radiating  like  the  fingers; 
said  of  the  veins  or  divisions  of  some  leaves. 

Panicle  (a  tuft).  A  loose  and  irregularly  branching  flower- 
cluster,  as  in  many  grasses. 

Pappus  (down).     The  modified  calyx  of  the  Composites. 

Paraphysis,  pi.  paraphyses  (accompanying  organs).  Sterile 
bodies,  usually  hairs,  which  are  found  mingled  with  the 
reproductive  organs  of  various  Cryptogams. 

Parasite.  An  organism  that  obtains  its  food  from  other  living 
organisms. 

Parenchyma  (that  which  pours  in  beside).  Ordinary  or  typical 
cellular  tissue,  i.e.,  of  thin- walled,  nearly  isodiametric  cells. 

Parthenogenesis  (virgin  generation).  The  formation,  without 
fertilization,  of  a  spore  which  is  functionally  the  same  as 
a  sexual  spore.  In  general  it  means  that  the  female 
gamete  becomes  a  spore  directly. 

Pedicel  (a  little  foot).  The  stalk  upon  which  an  organ  is 
borne. 

Peduncle  (a  little  foot).     The  flower-stalk. 

Pentacyclic  (five  cycles).  Applied  to  flowers  whose  four  kinds 
of  floral  organs  are  in  five  cycles. 

Perianth  (around  the  flower).  The  floral  envelopes,  or  leaves 
of  a  flower,  taken  collectively;  and  an  analogous  envelope 
of  the  sporogonium  of  certain  liverworts. 

Periblem  (a  cloak).  A  name  given  to  that  part  of  the  meri- 
stem  at  the  growing  point  of  the  plant-axis,  which  lies 
just  beneath  the  epidermis  and  develops  into  the  cortex. 

Pericambium  (surrounding  growing  tissue).  In  roots,  the 
external  layer  of  the  fibro-vascular  cvlinder. 

Perichaetium,  pi.  perichatia  (surrounding  hairs  or  leaves).  In 
Bryophytes,  the  leaves  or  leaf-like  parts  which  envelop  the 
clusters  of  sex-organs,  forming  in  some  cases  the  so-called 
flower. 

Perigynous  (around  the  ovary).  Applied  to  those  flowers 
whose  parts  arise  from  around  the  wall  of  the  ovary. 

Peristome  (around  the  mouth).  In  mosses,  usually  bristle- 
like  or  tooth-like  structures  surrounding  the  orifice  of  the 
capsule. 


182  GLOSSARY. 

Perithecium,  pi.  perithecia  (around  the  case).  The  spore- 
vessel  of  certain  Carpophytes,  containing  the  spore-sacs 
(asci). 

Petal  (a  leaf).     A  corolla-leaf. 

Petiole  (a  little  foot).     The  stalk  of  a  leaf. 

Phanerogamia  (evident  marriage).  A  primary  division  (the 
highest)  of  plants,  named,  from  their  mode  of  reproduc- 
tion, the  seed-producing  plants.  Phanerogam  is  the 
English  equivalent.  See  Spermatophytes. 

Phloem  (the  inner  bark).  The  bark  or  bast  portion  of  a  fibro- 
vascular  bundle. 

Photosynthesis  (light  construction).  The  name  applied  to  the 
process  through  which  chloroplasts  under  the  influence  of 
sunlight  manufacture  such  carbohydrates  as  starch  and 
sugar  from  water  and  carbon  dioxid. 

Phycocyanin  (blue  seaweed).  A  bluish  coloring-matter  found 
within  certain  Algas. 

Phyllotaxy.     Leaf-arrangement. 

Pinna,  pi.  pinna  (a  feather).  One  of  the  primary  divisions 
of  a  pinnate  leaf,  as  in  ferns. 

Pinnule  (a  little  feather).     One  of  the  divisions  of  a  pinna. 

Pistil  (a  pestle).  A  simple  or  compound  carpel  in  Spermato- 
phytes. 

Pit.  A  thin  place,  or  pit-like  depression,  left  in  the  thickening 
of  a  cell-wall. 

Placenta,  pi.  placentae  (a  cake).  That  portion  of  the  ovary 
which  bears  the  ovules. 

Plerome  (that  which  fills).  A  name  given  to  that  part  of 
the  meristem,  near  the  growing  points  of  the  plant-axis, 
which  forms  a  central  shaft  or  cylinder  and  develops  into 
the  axial  tissues. 

Plumule  (a  little  feather).  The  terminal  bud  of  the  embryo 
above  the  cotyledons. 

Pod.  A  dry,  several-seeded,  dehiscent  fruit;  or  a  similar  spore- 
case. 

Pollen  (fine  flour).     The  spores  developed  in  the  anther. 

Pollen-tube.  The  structure  that  develops  from  the  wall  of 
the  microspore  on  Spermatophytes  and  carries  male  cells 
to  the  egg. 

Pollination.     The  transfer  of  pollen  to  the  stigma. 

Polypetalous  (many  petals).  Applied  to  flowers  that  have 
their  petals  free  from  one  another, 


GLOSSARY.  183 

Proembryo  (going  before  the  embryo).  In  Spermatophytes, 
the  chain  of  cells  (suspensor)  formed  after  fertilization, 
and  from  the  lower  end  of  which  the  embryo  develops 
See  Suspensor. 

Prothallium,  pi.  prothallia  (a  forerunning  shoot).  The  small, 
usually  short-lived  plant  which  develops  from  the  spore 
and  bears  the  sex-organs. 

Protonema,  pi.  protonemata  (that  which  is  first  sent  out).  In 
mosses,  the  filamentous  growth  which  is  produced  by  the 
spores,  and  from  which  the  leafy  moss-plant  is  developed. 

Protophyta  (the  first  plants).  A  primary  division  of  plants 
named  from  the  fact  that  they  include  the  lowest  known 
plants.  Protophyte  is  the  English  equivalent. 

Protoplasm  (that  which  is  first  formed).  The  living  matter  of 
cells. 

Pteridoid.     Fern-like. 

Pteridophyta  (fern-plants).  A  primary  division  of  plants, 
named  from  its  principal  group,  the  ferns.  Pteridophyte 
is  the  English  equivalent. 

Pyrenoid  (kernel-formed).  Minute  colorless  bodies  imbedded 
in  the  chlorophyll  structures  of  some  lower  plants. 

Raphides  (needle-formed).     Needle-like  plant-crystals. 

Receptacle.  That  portion  of  an  axis  or  pedicel  (usually 
broadened)  which  forms  a  common  support  for  a  cluster 
of  organs,  either  sex-organs  or  sporophylls. 

Reticulated  (net-like).     Having  a  net-like  appearance. 

Rhachis  (the  backbone).  The  axis  of  a  compound  leaf,  or 
of  a  spike. 

Rhaphe  (a  seam).  In  an  anatropous  ovule,  the  ridge  which 
connects  the  chalaza  with  the  hilum. 

Rhizoid  (root-formed).  Root-like;  a  name  applied  to  the 
root-like  hairs  fomnd  in  Bryophytes  and  Pteridophytes. 

Rhizotaxy.     Root- arrangement. 

Root-stock.  A  horizontal,  more  or  less  thickened,  root-like 
stem,  either  on  the  ground  or  underground. 

Saprophyte  (rotten  plant).  Organisms  that  obtain  their  food 
from  dead  or  decaying  organisms. 

Scalariform  (ladder-form).  A  name  applied  to  ducts  with  pits 
horizontally  elongated  and  so  placed  that  the  intervening 
thickening  ridges  appear  like  the  rounds  of  a  ladder. 

Scale  (a  flight  of  steps).  Any  thin  scarious  body,  as  a  degen- 
erated leaf,  or  flat  trichome. 


1 84  GLOSSARY. 

Sclerenchyma  (a  hard  infusion).  A  tissue  belonging  to  the 
fundamental  system  and  composed  of  cells  that  are  thick- 
walled,  often  excessively  so. 

Scutellum  (a  small  dish).  The  disk-like  or  shield-like  cotyledon 
of  grasses. 

Seed.     The  matured  ovule. 

Sepal.     A  calyx-leaf. 

Seta,  pi.  setce.  A  bristle,  or  bristle-shaped  body;  in  mosses, 
the  stalk  of  the  capsule. 

Sexual  spore.     One  formed  by  the  union  of  cells. 

Sheath.  A  thin  enveloping  part,  as  of  a  filament,  leaf,  or 
resin-duct. 

Sieve-cells.  Cells  belonging  to  the  phloem,  and  characterized 
by  the  presence  of  circumscribed  and  perforated  panels 
in  the  walls;  the  panels  are  sieve-plates,  and  the  perfora- 
tions sieve-pores. 

Sorus,  pi.  sori  (a  heap).  In  ferns,  the  groups  of  sporangia, 
constituting  the  so-called  "fruit-dots";  in  parasitic  Fungi 
well-defined  groups  of  spores,  breaking  through  the  epider- 
mis of  the  host. 

Sperm,  or  Spermatozoid  (animal-like  sperm).  The  male 
gamete. 

Spermatophytes  (seed-plants).  The  highest  great  group  of 
plants,  of  which  a  characteristic  structure  is  the  seed. 

Spike  (an  ear  of  corn).  A  flower-cluster,  having  its  flowers  ses- 
sile on  an  elongated  axis. 

Spikelet  (diminutive  of  spike).  A  secondary  spike;  in  grasses, 
the  ultimate  flower-cluster,  consisting  of  one  or  more 
flowers  subtended  by  a  common  pair  of  glumes. 

Sporangium,  pi.  sporangia  (spore- vessel).  The  spore-produc- 
ing structure. 

Spore  (seed).  Originally  used  as  the  analogue  of  seed  in 
flowerles  plants;  now  applied  to  any  one-celled  or  few- 
celled  body  which  is  separated  from  the  parent  for  the 
purpose  of  reproduction,  whether  sexually  or  asexually 
produced;  the  different  methods  of  its  production  are 
indicated  by  suitable  prefixes. 

Sporogonium,  pi.  sporogonia  (spore-offspring).  The  whole 
structure  of  the  spore-bearing  stage  of  Bryophytes. 

Sporophyll.     A  leaf  that  bears  sporangia. 

Sporophyte  (spore-plant).  The  asexual  or  spore-producing 
stage  of  an  alternating  plant. 


GLOSSARY.  185 

Stamen  (the  warp,  or  thread,  of  cloth).     The  microsporophyll 

in  Spe.vmatophytes. 
Stigma   (a  spot  or  mark).     The  surface  of  a  pistil  without 

epidermis  which  receives  the  pollen. 
Stigmatic.     Relating  to  the  stigma,  or  stigma-like. 
Stoma,  pi.    stomata   (a  mouth).     Epidermal  structures  which 

serve  for  facilitating  gaseous  interchanges  with  the  exter- 
nal   air,    and    for   transpiration    of   moisture.     They    are 

often  called  "breathing-pores." 
Strobilus.     A  cone- like  cluster  of  sporophylls. 
Strophiole  (a  small  wreath).     An  appendage  at  the  hilum  of 

certain  seeds. 
Style  (a  pillar).     The  usually  attenuated  portion  of  the  pistil 

which  bears  the  stigma. 
Suspensor.     A  chain  of  cells  which  develops  early  from  the 

oospore   and  serves  to  push  the  embryo-cell  deep  within 

the  embryo-sac. 
Symbiont.     One    of  the  organisms  that    has    entered  into  a 

symbiotic  relationship. 
Symbiosis     (living  together).     Applied  to   a  condition   where 

two  or  more  organisms  are  living  in  an  intimate  relation- 
ship. 
Syncarpous    (carpels    united).     Applied    to    those    conditions 

where  the  carpels  have  united  into  a  compound  pistil. 
Synerigdae,  or  Synergides  (helpers).     The  two  nucleated  bodies 

which  accompany  the  oosphere  in  the  embryo-sac,  and 

together  with  it  form  the  egg-apparatus. 
Testa  (a  shell).     The  outer  seed-coat. 
Tetracyclic  (four  cycles).     Applied  to  those  flowers  in  which 

there  are  four  cycles  of  floral  organs. 
Tetradynamous     (four-strong).     Said     of     an     andrcecium    in 

which  there  are  four  long  and  two  shorter  stamens. 
Thalloid.     Thallus-like. 
Thallus   (a  young  shoot).     The  body  of  lower  plants,  which 

exhibits  no  differentiation  of  stem,  leaf,  and  root. 
Theca,    pi.   thecce   (a  case).     The   "anther-cell,"   that   is,   the 

case  containing  pollen;    sometimes  used  of  other  spore- 
cases. 
Tracheary  tissue.     A  general  name  given  to  the  vessels  and 

ducts  found  in  fibro-vascular  bundles. 
Tracheides   (rough-formed  tissues).     Tracheary  cells  that  are 

closed  throughout. 


1 86  GLOSSARY. 

Trichogyne.  A  hair-like  extension  from  the  bulbous  portion 
of  the  oogonium,  found  in  many  red  Algae. 

Trichome  (a  hair).  A  general  name  for  a  slender]  outgrowth 
from  the  epidermis,  usually  arising  from  a  single  cell. 

Turgidity.  The  normal  swollen  condition  of  active  cells  which 
results  from  the  distension  brought  about  by  absorption 
of  water. 

Vein.     The  fibro- vascular  bundle  of  leaves  or  any  flat  organ. 

Venation.     The  mode  of  vein-distribution. 

Xylem  (wood).  The  wood  (inner)  portion  of  the  fibro- vascular 
bundle. 

Zoospore  (animal  spore) .     A  motile  asexual  spore. 

Zygomorphic.  Said  of  a  flower  which  can  be  bisected  by 
only  one  plane  into  similar  halves. 

Zygophyta  (yoke-plants).  A  primary  division  of  plants,  now 
commonly  spoken  of  as  Conjugate,  named  from  their  mode 
of  reproduction,  the  sexual  spore  being  produced  by  con- 
jugation. Zygophyte  is  the  English  equivalent. 

Zygospore  (yoke-spore).  The  spore  of  Conjugate,  formed  by 
conjugation. 


INDEX. 


Achillea  millefolium,  171 
Achlorous,  87 

Bergen,  J.  Y.,  IT 
Books  of  reference,  10 

Adiantum  pedatum,  108 

Bordered  pits,  134 

Aerial  stem,  146 

Bracken  fern,  107 

Agaricus,  57 

Britton  and  Brown,  u,  154 

Albugo,  7,  62 

Bryales,  99 

Alcohol,  2 

Bryophytes,  80 

Algae,  16 

Bundle-sheath,  136 

Allium,  145 

Buttercup,  158 

Alternation  of  generations,  83,  84, 

114 

Caltha,  158 

Amarantus  retroflexus,  62 

Calyptra,  103 

Angiosperms,  128,  145 

Calyx,  147 

Annual  growth  rings,  162 

Cambium,  150 

Annulus,  in 

Campbell,  D.  H.,  n 

Anther,  147 

Canal  cells,  82 

Antheridium,  48 

Capsella  bursa-pastoris,  62,  157 

Anthoceros,  7,  95 

Capsule,  89 

Anthocerotales,  95 

Carpel,  147 

Antipodal  cells,  153 

Carpellate,  130 

Apical  cell,  no 

Carpogonium,  72 

Apothecium,  75 

Chalazogamy,  154 

Appendages  on  lilac  mildew,  71 
Araceae,  159 

Champia  parvula,  54 
Chamberlain,   C.  J.,   3,    n,   132, 

Archegonium,  81 

r34 

Ascocarps,  70 

Chapman,  A.,  n 

Ascomycetes,  69 

Chester,  Grace  D.,  54                . 

Ascospores,  72 

Chlor-iodide  of  zinc,  19 

Ascus,  71 

Chlorophyceae,  16 

Atkinsion,  G.  F.,  n 

Chlorophyll,  16 

Atricum  undulatum,  99 

Chlorophyllose,  87 

Chloroplasts,  18 

Bailey,  L.  H.,  n 

Chrysanthemum,  167 

Balsaminese,  159 

Cilia,  20 

Barnes,  C.  R.,  n 

Cladonia,  75 

Basidia,  60 

Cladophora,  29,  34 

Basidiophore,  61 

Clatherocystis,  21 

Basidiomycetes,  61 

Closed  bundle,  109,  150,  157 

Batrachospermum,  54,  73 

Club-moss,  122 

187 

i88 


INDEX. 


Ccenocyte,  35 

Fertilization,  49 

Coleochaete,  51 

Fertilizing  tube,  65 

Collection  of  material,  13  * 

Fibrovascular  regions,  109 

Columella.  57 

Filicales,  107 

Compositae,  167 

Filicineae,  107 

Cones,  132 

Flower,  146 

Conidia,  63 

Formalin,  use  of,  14 

Conidiospores,  63 
Coniferales,  129 
Conjugation,  33,  57 
Conjugating  tubes,  41 

Funaria  hygrometrica,  99 
Functions  of  plants,  i 
Fungi,  1  6,  55 

Conocephalus  conatus,  85 
Construction  of  foods,  43] 

Gamete,  33 
Gametophyte,  90 

Convolvulaceae,  159 

Gemmae,  86 

Coprinus,  59 

Generative  cells,  153 

Corolla,  147 

Gills,  60 

Cortex,  149 

Gill-chambers,  60 

Cotyledons,  139 
Coulter,  J.  M.,  n,  132,  144 

Glassware,  2,  3 
Glceocapsa,  21 

Cruciferae,  159 

Glcetrichia,  21 

Cupules,  87 

Glycerin  mounts,  7 

Cuticle,  135 

Goebel,  K.,  12 

Cyanophyceae,  21 

Gramineae,  159 

Cycle,  Floral,  145' 

Gray,  Asa,  12,  154 

Cylindrospermum,  21 

Growth  rings,  131 

Grout,  A.  J.,  12 

Davis,  B.  M.,  54,  84,  98 

Guard  cells,  in 

DeBary,  A.,  12 

Dehiscence,  152 

Hand  lens,  4 

Dermatogen,  148 

Harper,  R.  A.,  72 

Dicotyledons,  150,  158 

Haustorium,  64 

Dioecious,  104 

Helianthus  annuus,  167 

Dissecting  instruments,  3 
Dorsi-ventral,  94 

Hepaticae,  80 
Herbarium  specimens,  8 

Drawing  materials,  3 

Heterocyst,  22 

Heterosporous,  126 

Elaters,  90,  1  19  '  ' 

Holdfast,  37 

Embryo,  114 

Homosporous,  125 

5mbryo-sac,  139 

Hydroxids,  2 

Endogenous,  96 

Hypha,  56 

Endosperm  nucleus,  153 

Hypoderma,  136 

Environment,  i 

Hypogynous,  148 

Epigynous,  170 

Equipment,  2 

Imbedding,  etc.,  16 

Equisetales,  117 

Independent  work,  14. 

Equisetineae,  117 

Indusium,  109 

Equisetum  arvense,  117 

Inflorescence,  168 

Euphorbiaceae,  159 

Integument,  138 

Evolution,  i 

Internode,  109 

Isogamous,  44 

Farmer,  J.  B.,  54 

Involucre,  169 

INDEX. 


189 


Jungermanniales,  93 

Oosphere,  48 

Oospore,  48 

Laboratory,  2,  4 

Operculum,  103 

Lamina,  159 

Oscillatoria,  24 

Leguminosse,  159 

Ovary,  147 

Lepidium,  62 

Ovules,  138 

Leptosporangiate,  116 

Lichen,  75 
Lilac  mildew,  69 

Palisade,  151 
Paraphyses,  60,  77 

Liliacese,  145 

Parasite,  67 

Liverwort,  80 

Parmelia,  75 

Lunularia  cruciata,  86 

Parthenogenesis,  72 

Lycopodiales,  122 

Perianth,  89 

Lyon,  Florence  M.,  128 

Periblem,  149 

Perigynous,  170 

Magnification,  4 

Peristome,  103 

Malvaceae,  159 

Permanent  mounts,  3 

Marchantia,  7,  85 

Petiole,  109 

Marchantiales,  85 

Pfeffer,  W.,  12 

Marsilia,  7,  124,  125 

Phaeophyceae,  54 

Medullary  rays,  133 

Phloem,  109 

Megaspore,  124 

Phloem  parenchyma,  134 

Magasporangiate,  129 

Photographs,  9 

Magasporophyll,  131 

Photosynthesis,  43 

Meristem,  148 

Phycomycetes,  55 

Mesophyll,  in 

Physcia,  75 

Micropyle,  139 

Pileus,  59 

Microscopes,  4 

Pmaceae,  129 

Microsphaera,  69 

Pine,  7,  129 

Microspore,  124 

Pistil,  147 

Microsporangiate,  130 

Plerome,  149 

Microsporophyll,  137 

Pleurococcus,  16 

Microtome,  6 

Pollen,  130 

Monocotyledons,  145 

Pollen-sac,  152 

Monoecious,  104 

Pollination,  139 

Moss,  7,  99 

Porella,  7,  92 

Mucor,  55 

Portulaca  oleraceae,  62 

Musci,  99 

Potassium  hydroxid,  2 

Mushrooms,  59 

Primary  endosperm  nucleus,  153 

Mycelium,  56 

Prothallium,  112 

Protonema,  101 

Nasturtium,  62 

Protoplasm,  18 

Nemalion  multifidum,  54,  73 

Pteris,  7,  107 

Nodes,  109 

Pteridophytes,  109 

Nostoc,  21 

Pyrenoids,  32 

Nucellus,  139 

Pyronema  confluens,  72 

Nucleus,  18 

Nutrition,  i 

Ranunculaceae,  158 

Ranunculus,  7,  158 

Oltmanns,  E.,  52 

Raphanus,  62 

Oogonium,  47 

Reagents,  3 

igo 


INDEX. 


Receptacle,  148 

Sterigma,  60 

Reference  reading,  10 

Stele,  149 

Reproduction,  i 

Stevens,  F.  L.,  65 

Resin-ducts,  133 

Stigma,  148 

Rhizome,  108 

Stipe,  59 

Rhizoids,  56 

Stoma,  in,  136 

Rhizopus,  55 

Strasburger,  E.,  12 

Rhodophyceaj,  54 

Strobilus,  123 

Riccia,  80 

Style,  147 

Ricciales,  80 

Sunflower,  167 

Ricciocarpus  natans,  80 

Suspensor,  125 

Rivularia,  21 

Synergids,  153 

Root-cap,  108 

Syngenesious,  169 

Rosaceae,  159 

Synthol,  2 

Rudbeckia,  167 

Tables,  2 

Salicaceae,  159 

Taraxacum,  167 

Sclerenchyma,  109 
Scouring  rush,  117 

Tetradynamous,  165 
Text-books,  n 

Seed,  144 
Selaginella,  7,  122 
Selaginellaceae,  122 

Thallophytes,  16 
Toad-stools,  59 
Tracheae,  140 

Sepal,  147 

Tracheids,  133 

Seta,  102 
Seward,  A.  C.,  121 

Trichogyne,  52 
Trillium,  7    145 

Shepherd's-purse,  159 
Sieve-cells,  134 
Silphium,  167 

Tube  nucleus,  152 
Turgidity,  26,  27 

Sinapis,  62 
Sisymbrium,  62 
Small,  J.  K.,  12 
Smith,  Grant,  73 
Sodium  hydroxid,  2 

Ulothrix,  29 
Umbelliferas,  159 
Underwood,  L.  M.,  12 
Usnea  barbata,  79 

Solidago,  167 

Solonaceae,  159 

Valves  of  capsule,  94 

Sorus,  63,  109 

Vascular  bundles,  109,  133 

Sperm,  48 

Vaucheria,  46 

Sperm  mother-cells,  82 
Spermatophytes,  122 

Vegetative  reproduction,  18 
Veil  of  toadstool,  60 

Spirogyra,  38 

Venation,  109 

Sporangiophore,  56 
Sporangium,  56 

Venter,  89 
Ventral  canal  cell,  81 

Spore,  31 

Sporocarp,  125 

Wake-robin,  145 

Sporogenous,  83 

Williams,  J.  L.,  54 

Sporogonium,  82 

Sporophylls,  118 

Zea  mais,  149 

Sporophytes,  80,  83 

Zoospore,  20 

Stamen,  137 

Zygnema,  43 

Staminate,  130 

Zygospore,  33 

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